Patent Publication Number: US-11653184-B2

Title: Call prompt method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/067,244, filed on Jun. 29, 2018, which is a national stage of International Application No. PCT/CN2015/100178, filed on Dec. 31, 2015. Both of the aforementioned applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the communications field, and in particular, to a call prompt method. 
     BACKGROUND 
     As communications technologies develop, voice communication becomes a basic daily communication manner of people. A mobile terminal interacts with a network based on a communications protocol, so as to implement voice communication between different users. 
     A current voice call has some problems that trouble users. For example, a user A uses a mobile phone A, a user B uses a mobile phone B, and a user C uses a mobile phone C. When the mobile phone A and the mobile phone B that communicate based on a CDMA (Code Division Multiple Access, Code Division Multiple Access) communications standard are in a call state, if the mobile phone C calls the mobile phone A, the user A hears constant prompt tones “beep” while hearing a voice of the user B, and a prompt of the call from the mobile phone C is displayed on a user interface of the mobile phone A. The user A may cut off the call from the mobile phone C. However, after the user A cuts off the call from the mobile phone C, the prompt tone “beep” from the mobile phone A does not disappear. 
     In addition, after the mobile phone A detects the call from the mobile phone C, if the mobile phone C abandons the call, the prompt tone on the mobile phone A disappears, but the call interface indicating that the mobile phone C initiates a call is still displayed. If the user A selects to answer the call, because the mobile phone C has abandoned the call, the call between the mobile phone A and the mobile phone C cannot be actually established, the call between the mobile phone A, and the mobile phone B is suspended. 
     Voice calls are almost indispensable to people&#39;s daily life. If the foregoing case occurs for multiple times or even frequently, a trouble is certainly brought to the users. Therefore, for the foregoing symptom, how to eliminate interference caused by the unconnected new call to the current call when the mobile phone A is in a call state is an urgent problem that needs to be resolved. 
     SUMMARY 
     Embodiments of the present invention provide a call prompt method, so as to resolve an existing problem, that is, to eliminate interference caused when a call initiated by a mobile phone C is unconnected in a process of a call between a mobile phone A and a mobile phone B. 
     According to a first aspect, an embodiment of the present invention provides a call prompt method in a CDMA communications network, including: 
     displaying a first interface on a display screen of a first terminal, where the first interface shows that a first terminal is in a call with a second terminal; 
     displaying a second interface on the display screen of the first terminal, where the second interface prompts that a third terminal initiates a call to the first terminal, and at this moment, the first terminal is still in a call with the second terminal; 
     outputting, on the first terminal, a sound, where the sound includes a prompt tone and a call voice between the first terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the first terminal; and 
     if the call initiated by the third terminal to the first terminal is rejected, continuing outputting, on the first terminal, the call voice between the first terminal and the second terminal, and stopping outputting the prompt tone; 
     if the third terminal stops initiating the call to the first terminal, displaying the first interface on the display screen of the first terminal, and continuing outputting, on the first terminal, the call voice between the first terminal and the second terminal. 
     According to the method provided in the first aspect of the present invention, in a process of the call between the first terminal and the second terminal, the third terminal initiates a call to the first terminal. If the first terminal rejects the call initiated by the third terminal, the first terminal no longer outputs a prompt tone “beep” while normally outputting the call voice between the first terminal and the second terminal. In this way, after rejecting the call initiated by the third terminal, a user eliminates impact of the rejected call on the current call in a timely manner. Alternatively, after the third terminal stops the call to the first terminal, the first terminal may return an interface of the call between the first terminal and the second terminal in a timely manner, so as to prevent the user from answering the call that cannot be actually connected and that is initiated by the third terminal. This avoids interference caused by the call interface to the current call. 
     With reference to the first aspect, in a first implementation of the first aspect, the first terminal determines, by detecting that the prompt tone disappears, that the third terminal stops initiating the call to the first terminal. 
     In a current communications standard, after the third terminal stops initiating the call to the first terminal, a network does not send a notification message to the first terminal, and the first terminal cannot directly learn whether the third terminal stops the call. However, it is learned, by means of analysis, that after the third terminal stops the call, a downlink signal received by the first terminal does not include a prompt tone. Therefore, the first terminal may determine, by detecting whether the downlink signal includes a prompt tone, whether the third terminal stops the call. 
     With reference to the first implementation of the first aspect, in a second implementation of the first aspect, the detecting, by the first terminal, that the prompt tone disappears specifically includes: 
     if the first terminal detects no prompt tone in N prompt tone detection periods, determining that the prompt tone disappears, where N is greater than or equal to 2. 
     The prompt tone is a signal that appears at equal time intervals. If no prompt tone is detected in a preset quantity of periods, the first terminal determines that the call prompt tone disappears, and further determines that the third terminal stops the call. 
     With reference to the first aspect, in a third implementation of the first aspect, the first terminal stops outputting the prompt tone by changing an amplitude value of a frequency corresponding to the prompt tone. 
     All voice signals have specific time-frequency characteristics. The prompt tone is also a type of voice signal. If a spectrum characteristic of the prompt tone can be learned, the prompt tone may be eliminated by changing, at the frequency corresponding to the prompt tone, the amplitude value of the frequency, so that the first terminal stops outputting the prompt tone. 
     With reference to the first or the second implementation of the first aspect, in a fourth implementation of the first aspect, that the first terminal detects the prompt tone includes: 
     parsing, by the first terminal, a system broadcast message of a current cell to obtain network information, obtaining, according to the network information, prompt tone information pre-stored in the first terminal, and then detecting a prompt tone in a received downlink signal according to the pre-stored prompt tone information. 
     If the pre-stored prompt tone information is corresponding to prompt tone information in the downlink signal, the first terminal may detect the prompt tone by using the system broadcast message. This is easy to implement. 
     With reference to the fourth implementation of the first aspect, in a fifth implementation of the first aspect, the network information includes a home operator network and a network standard. 
     With reference to the first or the second implementation of the first aspect, in a sixth implementation of the first aspect, the first terminal detects the prompt tone by using a linear spectrum detection method. 
     With reference to the sixth implementation of the first aspect, in a seventh implementation of the first aspect, a fundamental frequency of the prompt tone is a single-frequency tone that has a constant amplitude and a constant frequency; and the detecting, by the mobile terminal, the prompt tone by using a linear spectrum detection method includes: 
     performing, by the first terminal, channel decoding and voice decoding on the received downlink signal, so as to obtain pulse code modulation PCM data; 
     dividing the PCM data into multiple overlapping data frames; 
     multiplying each of the multiple data frames by a window function, and performing a Fourier transformation, so as to obtain a complex spectrum; 
     calculating, at each pre-estimated frequency, a correlation coefficient between complex spectra of a previous frame and a current frame in a relaxation period; and 
     determining, by the first terminal, that the prompt tone is detected on a corresponding frequency if the correlation coefficient exceeds a preset threshold. 
     By using a linear spectrum detection method to detect the prompt tone, prompt tones in different communications standards can be detected. This method is quite generic, and has high detection accuracy. 
     With reference to the seventh implementation of the first aspect, in an eighth implementation of the first aspect, after the first terminal receives the call initiated by the third terminal, the method further includes: obtaining, according to network information obtained by the first terminal by parsing a system broadcast message of a current cell, prompt tone information pre-stored in the first terminal, and then detecting a prompt tone in the downlink signal according to the pre-stored prompt tone information; and 
     after the determining, by the first terminal, that the prompt tone is detected on a corresponding frequency if the correlation coefficient exceeds a preset threshold, the method further includes: 
     comparing a frequency and an amplitude of the detected prompt tone with a frequency and an amplitude in the prompt tone information pre-stored in the first terminal, and if a comparison result is that the frequency and the amplitude of the detected prompt tone are the same as the frequency and the amplitude in the prompt tone information pre-stored in the first terminal, or differences between the frequency and the amplitude of the detected prompt tone and the frequency and the amplitude in the prompt tone information pre-stored in the first terminal do not exceed comparison thresholds, determining, by the mobile terminal, that the prompt tone is detected. 
     With the solution in which a comparison is further performed, accuracy of prompt tone detection may be improved. 
     According to a second aspect, an embodiment of the present invention provides a terminal used in a Code Division Multiple Access CDMA communications network, including: 
     a display module, configured to display a first interface, where the first interface shows that the terminal is in a call with a second terminal, where 
     the display module is further configured to display a second interface, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     a processing module, configured to detect whether the call initiated by the third terminal to the terminal is rejected, where 
     the processing module is further configured to detect whether the third terminal stops initiating the call to the terminal; and 
     an output module, configured to output a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal, where 
     the output module is further configured to: when the processing module detects that the call initiated by the third terminal to the terminal is rejected, continue outputting the call voice between the terminal and the second terminal, and stop outputting the prompt tone; or 
     when the processing module detects that the third terminal stops initiating the call to the terminal, continue outputting the call voice between the first terminal and the second terminal; and 
     the display module is further configured to: when the processing module detects that the third terminal stops initiating the call to the terminal, and the output module continues outputting the call voice between the first terminal and the second terminal, display the first interface. 
     According to the terminal provided in the second aspect of the present invention, in a process of the call between the terminal and the second terminal, the third terminal initiates a call to the terminal. If the terminal rejects the call initiated by the third terminal, the terminal no longer outputs a prompt tone “beep” while normally outputting the call voice between the terminal and the second terminal. In this way, after rejecting the call initiated by the third terminal, a user eliminates impact of the rejected call on the current call in a timely manner. Alternatively, after the third terminal stops the call to the terminal, the terminal may return an interface of the call between the terminal and the second terminal in a timely manner, so as to prevent the user from answering the call that cannot be actually connected and that is initiated by the third terminal. This avoids interference caused by the call interface to the current call. 
     The terminal provided in the second aspect of the present invention may be further configured to implement the first to the eighth implementations of the call prompt method in the first aspect, and details are not described herein again. 
     According to a third aspect, an embodiment of the present invention provides a processor used in a CDMA communications network, where the processor is configured to perform the following operations: 
     controlling to display a first interface, where the first interface shows that the terminal is in a call with a second terminal; 
     controlling to display a second interface, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     outputting a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; 
     if the call initiated by the third terminal to the terminal is rejected, continuing outputting the call voice between the terminal and the second terminal, and stopping outputting the prompt tone; and/or 
     if the third terminal stops initiating the call to the terminal, controlling to display the first interface, and continuing outputting, on the terminal, the call voice between the terminal and the second terminal. 
     The processor provided in the third aspect of the present invention can implement the call prompt method in the first aspect. By using the processor, after rejecting the call initiated by the third terminal, a user may eliminate impact of the rejected call on the current call in a timely manner. Alternatively, after the third terminal stops the call to the terminal, the terminal may return an interface of the call between the terminal and the second terminal in a timely manner, so as to prevent the user from answering the call that cannot be actually connected and that is initiated by the third terminal. This avoids interference caused by the call interface to the current call. 
     The processor provided in the third aspect of the present invention may be fuither configured to implement the first to the eighth implementations of the call prompt method in the first aspect, and details are not described herein again. 
     According to a fourth aspect, an embodiment of the present invention provides a terminal used in a CDMA communications network, where the terminal includes: 
     a transceiver, configured to communicate with a network device; 
     a display screen, configured to display information and receive user input; 
     a memory; and 
     a processor, configured to invoke one or more programs stored in the memory, so as to perform the following operations: 
     displaying a first interface on the display screen, where the first interface shows that the terminal is in a call with a second terminal; 
     displaying a second interface on the display screen, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     outputting, on the terminal, a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; and 
     if the call initiated by the third terminal to the terminal is rejected, continuing outputting, on the terminal, the call voice between the terminal and the second terminal, and stopping outputting the prompt tone; and/or 
     if the third terminal stops initiating the call to the terminal, displaying the first interface on the display screen of the terminal, and continuing outputting, on the terminal, the call voice between the terminal and the second terminal. 
     According to the terminal provided in the fourth aspect of the present invention, in a process of the call between the terminal and the second terminal, the third terminal initiates a call to the terminal. If the terminal rejects the call initiated by the third terminal, the terminal no longer outputs a prompt tone “beep” while normally outputting the call voice between the terminal and the second terminal. In this way, after rejecting the call initiated by the third terminal, a user eliminates impact of the rejected call on the current call in a timely manner. Alternatively, after the third terminal stops the call to the terminal, the terminal may return an interface of the call between the terminal and the second terminal in a timely manner, so as to prevent the user from answering the call that cannot be actually connected and that is initiated by the third terminal. This avoids interference caused by the call interface to the current call. 
     The terminal provided in the fourth aspect of the present invention may be further configured to implement the first to the eighth implementations of the call prompt method in the first aspect, and details are not described herein again. 
     According to a fifth aspect, an embodiment of the present invention provides a call prompt method, including: 
     displaying a first interface on a display screen of a first terminal, where the first interface shows that a first terminal is in a call with a second terminal; 
     displaying a second interface on the display screen of the first terminal, where the second interface prompts that a third terminal initiates a call to the first terminal, and at this moment, the first terminal is still in a call with the second terminal; 
     outputting, on the first terminal, a sound, where the sound includes a prompt tone and a call voice between the first terminal and the second terminal, the prompt tone is used to prompt a call event, and the call event indicates that the third terminal initiates a call to the first terminal; 
     if the call initiated by the third terminal to the first terminal is rejected, eliminating, by the first terminal, the prompt tone in a downlink signal, so as to continue outputting, on the first terminal, the call voice between the first terminal and the second terminal, and stop outputting the prompt tone to stop prompting the call event; and/or 
     if the first terminal detects, by detecting the prompt tone, that the third terminal stops initiating the call to the first terminal, stopping displaying the second interface on the display screen of the first terminal, displaying the first interface, and continuing outputting, on the first terminal, the call voice between the first terminal and the second terminal. 
     For other implementations of the call prompt method provided in the fifth aspect of the embodiments of the present invention, refer to the first to the eighth implementations of the call prompt method provided in the first aspect, and details are not described herein again. 
     According to a sixth aspect, an embodiment of the present invention provides a terminal, including: 
     a display module, configured to display a first interface, where the first interface shows that the terminal is in a call with a second terminal, where 
     the display module is further configured to display a second interface, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     a processing module, configured to detect whether the call initiated by the third terminal to the terminal is rejected, where 
     the processing module is further configured to detect whether the third terminal stops initiating the call to the terminal; and 
     an output module, configured to output a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal; and the prompt tone is used to prompt that the third terminal initiates a call to the terminal, where 
     the processing module is further configured to: when detecting that the call initiated by the third terminal to the terminal is rejected, eliminating the prompt tone in a downlink signal, so that the output module continues outputting the call voice between the terminal and the second terminal, and stops outputting the prompt tone; or 
     when the processing module detects, by detecting the prompt tone, that the third terminal stops initiating the call to the terminal, continue outputting the call voice between the first terminal and the second terminal: and 
     the display module is further configured to: when the processing module detects that the third terminal stops initiating the call to the terminal, and the output module continues outputting the call voice between the first terminal and the second terminal, display the first interface. 
     The terminal provided in the sixth aspect of the embodiments of the present invention may further correspondingly implement other implementations of the call prompt method in the fifth aspect, and details are not described herein again. 
     According to a seventh aspect, an embodiment of the present invention provides a processor, where the processor is configured to perform the following operations: 
     controlling to display a first interface, where the first interface shows that the terminal is in a call with a second terminal; 
     controlling to display a second interface, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     outputting a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; 
     if the call initiated by the third terminal to the terminal is rejected, eliminating, by the processor, the prompt tone in a downlink signal, so as to continue outputting the call voice between the terminal and the second terminal, and stop outputting the prompt tone; and/or 
     if the processor detects, by detecting the prompt tone, that the third terminal stops initiating the call to the terminal, controlling to display the first interface, and continuing outputting, on the terminal, the call voice between the terminal and the second terminal. 
     The processor provided in the seventh aspect of the present invention may be further configured to implement all other implementations of the call prompt method in the fifth aspect, and details are not described herein again. 
     According to an eighth aspect, an embodiment of the present invention provides a terminal, where the terminal includes: 
     a transceiver, configured to communicate with a network device; 
     a display screen, configured to display information and receive user input; 
     a memory; and 
     a processor, configured to invoke one or more programs stored in the memory, so as to perform the following operations: 
     displaying a first interface on the display screen, where the first interface shows that the terminal is in a call with a second terminal; 
     displaying a second interface on the display screen, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     outputting, on the terminal, a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; and 
     if the call initiated by the third terminal to the terminal is rejected, eliminating, by the terminal, the prompt tone in a downlink signal, so as to continue outputting, on the terminal, the call voice between the terminal and the second terminal, and stop outputting the prompt tone; and/or 
     if the terminal detects, by detecting the prompt tone, that the third terminal stops initiating the call to the terminal, displaying the first interface on the display screen of the terminal, and continuing outputting, on the terminal, the call voice between the terminal and the second terminal. 
     According to the method, the processor, and the terminal provided in the fifth to the eighth aspects of the present invention, in a process of the call between the first terminal and the second terminal, if the first terminal rejects the call initiated by the third terminal, the first terminal may eliminate the prompt tone in the downlink signal, and no longer outputs a prompt tone “beep” while normally outputting the call voice between the first terminal and the second terminal. In this way, after rejecting the call initiated by the third terminal, a user eliminates impact of the rejected call on the current call in a timely manner. Alternatively, the first terminal may perform prompt tone detection in real time; and after learning, by detecting the prompt tone, that the third terminal stops the call to the first terminal, the first terminal may return an interface of the call between the first terminal and the second terminal in a timely manner, so as to prevent the user from answering the call that cannot be actually connected and that is initiated by the third terminal. This avoids interference caused by the call interface to the current call. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To describe the technical solutions in the embodiments of the present invention more clearly, the following briefly describes the accompanying drawings required for describing the embodiments or the prior art. The accompanying drawings in the following description show merely some embodiments of the present invention, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings. 
         FIG.  1    is a schematic diagram of processing a downlink signal by a terminal disclosed in an embodiment of the present invention; 
         FIG.  2    is a schematic flowchart of a call prompt method disclosed in an embodiment of the present invention; 
         FIG.  3    is a schematic flowchart of another call prompt method disclosed in an embodiment of the present invention; 
         FIG.  4    is a schematic diagram of a prompt tone detection and elimination method disclosed in an embodiment of the present invention; 
         FIG.  5    is a schematic diagram of another prompt tone detection and elimination method disclosed in an embodiment of the present invention; 
         FIG.  6    is a schematic structural diagram of a terminal disclosed in an embodiment of the present invention; and 
         FIG.  7    is a schematic structural diagram of another terminal disclosed in an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the embodiments of the present invention in detail with reference to the accompanying drawings. To understand the present invention, the following detailed description mentions many specific details. However, a person skilled in the art should understand that the present invention may be implemented without these specific details. In other embodiments, well-known methods, processes, components, and circuits are not described in detail, so as to prevent the embodiments from being blurred. Apparently, the described embodiments are some rather than all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. 
     The terms used in the embodiments of the present invention are merely intended to better describe specific embodiments, and are not intended to limit the present invention. The terms “a”, “said”, and “the” of singular forms used in the embodiments and the appended claims of the present invention are also intended to include plural forms, unless otherwise specified in the context clearly. In the specification, claims, and accompanying drawings of the present invention, the terms “first”, “second”, “third”, and so on are intended to distinguish between different objects but do not indicate a particular order. It should also be understood that, the term “and/or” used herein indicates and includes any or all possible combinations of one or more associated listed items. It should be further understood that the term “include” adopted in the specification specifies presence of features, integers, steps, operations, elements and/or components, with presence or attachment of other features, integers, steps, operations, components, elements, and their combinations not excluded. 
     A mobile terminal used in the embodiments of the present invention may be a mobile terminal device that supports a CDMA communications standard and that has a mobile communications function, such as a mobile phone, a tablet computer, a personal digital assistant (Personal Digital Assistant, PDA for short), a point of sales (Point of Sales, POS for short), and a vehicle-mounted computer. This is not specifically limited in the embodiments of the present invention. 
     The CDMA communications standard in a CDMA communications network used in the embodiments of the present invention includes but is not limited to CDMA CDMA2000 1×, CDMA2000 2×, and CDMA2000 3×. The CDMA communications standard in the CDMA communications network used in the embodiments of the present invention does not include GSM (Global System of Mobile communication, Global System for Mobile Communications), WCDMA (Wideband Code Division Multiple Access, Wideband Code Division Multiple Access), Time Division-Synchronous Code Division Multiple Access (Time Division-Synchronous Code Division Multiple Access), and the like. Current CDMA-related standards are mainly formulated by the 3GPP2 (The 3rd Generation Partnership Project 2). The organization 3GPP2 was founded in January 1999, and was initiated by four standardization organizations: the TIA (USA), the ARIB (Japan), the TTC (Japan), and the TTA (South Korea). China Wireless Telecommunication Standard Group (CWTS) formally signed to join the 3GPP2 in South Korea in June 1999, and became a partner of this standardization organization that is mainly responsible for a third generation mobile communications technology CDMA2000. After China Communications Standards Association (CCSA) was founded, the CWTS was renamed CCSA in the organization 3GPP2. 
     Main work of the 3GPP2 is to formulate mobile communications technology specifications that are based on an ANSI-41 core network and in which CDMA2000 is used as a radio access network. Standard technology specifications include but are not limited to A.Sxxxx series, C.Sxxxx series, S.Sxxxx series, X.Sxxxx series, N.Sxxxx series, or the like, for example, 3GPP2 S.R0006-507-A. 
     It may be understood that the CDMA communications standard used in the embodiments of the present invention may not be limited to standards formulated by the 3GPP2, for example, may be another standard related to CDMA IS-95. 
     The mobile terminal used in the present invention may be a mobile phone. The following describes an embodiment of the present invention by using a mobile phone as an example. 
     It may be understood that, that a user A makes a call with a user B actually means that the user A uses a mobile phone A to make a call with a user B who uses a mobile phone B, and so on. The mobile phone A may also be referred to as a first terminal, the mobile phone B may also be referred to as a second terminal, and a mobile phone C may also be referred to as a third terminal. 
     When the mobile phone A and the mobile phone B are in a call state, if a call is received from the mobile phone C, a call voice of the mobile phone A is mixed up with a prompt tone “beep”. The prompt tone “beep” is a prompt tone that is sent by a network device and that indicates that the mobile phone A has a second call. For details about a related mechanism for carrying a prompt tone of another call in a call voice, refer to related content in the 3GPP2 S.R0006-507-A standard, and no detailed description is given in this specification. The network device mixes the prompt tone with a call voice of the mobile phone B that is in a first call, and a base station forwards the prompt tone and the call voice to the mobile phone A, Therefore, a downlink signal received by the mobile phone A includes the prompt tone. The network device may be a core network device, for example, an MSC (Mobile Switching Center, mobile switching center). The prompt tone “beep” in this application may be referred to as a beep tone or a prompt tone for short. 
     If the user A cuts off the call from the mobile phone C (for example, the user A selects, on an operation interface of the mobile phone A, to reject to answer the call from the mobile phone C), a display screen of the mobile phone A no longer displays a call interface of the call from the mobile phone C. However, if the mobile phone C does not stop the call, the downlink signal received by the mobile phone A still includes the prompt tone. That is, the beep tone on the mobile phone A continues and does not disappear. According to a thorough analysis made by the inventor of this application, this is because a notification message for cutting off another call in a call state is not stipulated in the CDMA communications standard. That is, the user A may select, on a user interface of the mobile phone A, to cut off the call from the mobile phone C, but the mobile phone A does not send a notification message for cutting off the call from the mobile phone C to a network. If the mobile phone A sends a cut-off message to the network, the network also cuts off the call between the mobile phone A and the mobile phone B. This is certainly not what is expected by the user A. 
     In addition, when the mobile phone C calls the mobile phone A, if the mobile phone A is in a call state, the mobile phone C may receive a prompt that indicates that the mobile phone A is in a call state and that is sent by the network. If a user C learns that the mobile phone A is in a call state, the user C may actively abandon the call from the mobile phone C to the mobile phone A. In this case, the prompt tone of the second call on the mobile phone A disappears, but an interface prompting the call from the mobile phone C is still displayed on a screen of the mobile phone A. According to a thorough analysis made by the inventor of this application, after the mobile phone C abandons the call to the mobile phone A, the network no longer prompts that the mobile phone A has a second call, the downlink signal received by the mobile phone A no longer includes the prompt tone of the second call, and the beep tone on the mobile phone A disappears. However, although the network no longer prompts that the mobile phone A has a second call, the network does not send a notification message to notify the mobile phone A that the second call from the mobile phone C has been abandoned. Therefore, the mobile phone A does not know that the call from the mobile phone C has been cut off, and still displays the call interface of the mobile phone C on the display screen, and the user A can select, on the call interface on the display screen of the mobile phone A, to answer the call. In this case, although the mobile phone A selects to answer the call from the mobile phone C, a real call connection cannot be established between the mobile phone A and the mobile phone C, and the call between the mobile phone A and the mobile phone B is suspended. This is certainly not what is expected by the user A, either. 
     If the foregoing case occurs frequently or for multiple times on the mobile phone A, experience of the user A is certainly greatly affected. 
     Optionally, the foregoing problem may be resolved by improving a network communications standard. For example, when the mobile phone A is in a call with the mobile phone B, if the mobile phone A cuts off the second call from the mobile phone C, the mobile phone A sends a first notification message to a network (for example, a CDMA wireless communications network), so as to notify the network that the call from the mobile phone C has been cut off. After receiving the first notification message, the network no longer sends to the mobile phone A the prompt tone of the call from the mobile phone C. In addition, the network can correctly recognize the first notification message, and does not cut off the call between the mobile phone A and the mobile phone B. In this case, the network may also notify the mobile phone C that the call is rejected, and release a call connection established between the network and the mobile phone C. 
     Optionally, after the network receives a message indicating that the mobile phone C abandons the call to the mobile phone A, the network may send a second notification message to notify the mobile phone A that the second call from the mobile phone C has been abandoned. After receiving the second notification message, the mobile phone A may automatically eliminate the call interface of the second call on the display screen of the mobile phone A, and returns to an interface of the first call between the mobile phone A and the mobile phone B. This process does not require user intervention, thereby improving user experience. 
     The foregoing first notification message and the second notification message may be added communication messages, or the notification messages may be identified by using an undefined field or an extended field in an existing exchanged message. This is not limited in this embodiment of the present invention. 
     By resolving the foregoing problem by using the network communications standard improvement solution, impact on the call between the mobile phone A and the mobile phone B from the unconnected call of the mobile phone C can be eradicated. However, in implementation of the foregoing solution, existing communications standards for a mobile phone and a network device need to be updated. 
     An embodiment of the present invention further provides a call prompt method to resolve the foregoing problem. Based on a communications standard of an existing CDMA communications network, the method is used to improve a terminal side to resolve the foregoing problem in a voice call. The call prompt method used in this embodiment of the present invention is a policy in which when a terminal receives a call, a prompt tone is output to prompt the call and/or a display interface indicates the call. 
     Referring to  FIG.  1   , an embodiment of the present invention provides a schematic diagram of processing a downlink signal by a terminal. In a process in which a user A makes a call with a user B, after an antenna  111  receives a downlink signal, a mobile phone A performs channel decoding on the downlink signal by using a channel decoding module  310 , and performs voice decoding on the downlink signal by using a voice decoding module  320 , so as to obtain pulse code modulation (Pulse Code Modulation, PCM) data. The methods for channel decoding and voice decoding are mature signal processing algorithms in the field, and details are not described in this embodiment of the present invention. It may be understood that the channel decoding module  310  and the voice decoding module  320  may be implemented by using a software algorithm, and may be software modules in a processor. 
     After obtaining the PCM data by performing channel decoding and voice decoding on the downlink signal, the mobile phone A processes the PCM data by using a downlink call audio algorithm module  350 , and then outputs a voice to the user. Specifically, the voice may be output to the user by using a receiver (Receiver, RCV)  562  or a microphone  562  that can output a voice, or may be output to the user by using a speaker  561  after the voice is amplified by using a power amplifier (Power Amplifier, PA)  163 . Processing performed by the downlink call audio algorithm module  350  on the PCM data may include noise suppression (Noise Suppression, NS), automatic gain control (Automatic Gain Control, AGC), dynamic range compression (Dynamic range compression, DRC), equalization (equalization, EQ), bandwidth expansion (Bandwidth Expansion, BEW), or the like. 
     It may be understood that when the mobile phone A makes a call with a mobile phone B, an uplink voice signal processing process may be considered as an inverse process of downlink voice signal processing. Processing performed by the downlink call audio algorithm module on a collected voice signal may include one or more of multi-microphone pickup, the NS, the AGC, the DRC, or the EQ, but is not limited thereto. After the collected voice signal is processed by using an uplink call audio algorithm module, voice encoding and channel encoding are performed on the collected voice signal, and then the collected voice signal is sent to a base station by using the antenna  111  on the mobile phone. The base station forwards the collected voice signal to another network device. 
     The mobile phone A implements voice signal receiving and sending functions on a mobile phone by processing an uplink signal and a downlink signal, so as to implement a normal call. 
     As shown in  FIG.  2   , an embodiment of the present invention discloses a call prompt method, so as to resolve the foregoing problem in an existing CDMA communications network. The method includes the following steps. 
     S 102 , When a mobile phone A is in a call state, display a first interface, where the first interface shows that the mobile phone A is in a call with a mobile phone B. 
     That the mobile phone A is in a call state means that the mobile phone A has established a first call with the mobile phone B. The first call may be triggered to be established when the mobile phone A calls the mobile phone B, or may be triggered to be established when the mobile phone A receives a call from the mobile phone B. 
     The mobile phone A interacts with a network by using a base station. The mobile phone A may receive, by using an antenna, a system broadcast message sent by the base station. The mobile phone A parses, based on a CDMA communications standard, the received system broadcast message, and may obtain information about a network that communicates with the mobile phone A, such as a home operator network and a network standard. The system broadcast message sent by the base station carries network information such as a home operator network and a cell ID, By parsing the received broadcast message, the mobile phone A can obtain the network information such as the home operator network and the network standard. 
     S 104 . If a second call is received, the mobile phone A displays a second interface on a display screen, where the second interface prompts that a mobile phone C initiates a call to the mobile phone A, and at this moment, the mobile phone A is still in a call with the mobile phone B; and the mobile phone A outputs a sound, where the sound includes a prompt tone and a call voice between the mobile phone A and the mobile phone B, the prompt tone is used to prompt a call event, and the call event indicates that the mobile phone C initiates a call to the mobile phone C. 
     If the second call from the mobile phone C is detected, the mobile phone A displays a call interface of the second call, that is, a second interface, on the display screen, and a user A hears a prompt tone “beep” while hearing a voice of a user B. 
     If the mobile phone C initiates the second call to the mobile phone A, a downlink signal received by the mobile phone A includes the call voice of the call between the mobile phone A and the mobile phone B, and the prompt tone of the second call initiated by the mobile phone C. 
     After the mobile phone A processes the received downlink signal by using a channel decoding module  310 , a voice decoding module  320 , and a downlink call audio algorithm module  350 , a speaker  561  or a receiver  562  outputs the downlink signal. 
     S 106 . The mobile phone A detects processing by a user on the second call, and if the user answers the second call, perform step S 108 , or if the user cuts off the second call, perform step S 110 . 
     After receiving the second call, the mobile phone A may detect, in real time, whether the user A answers or cuts off the second call. If it is detected that the user A performs no operation on the second call, the second call is not processed. If the mobile phone A detects an operation performed by the user A on the second call, the mobile phone A is triggered to process the second call, and S 108  or S 110  is performed. The user A may perform an operation on the second call on the display screen of the mobile phone A, or may trigger an operation instruction in another manner, for example, by pressing a button that is used for implementing answering or cut-off. This is not limited in this embodiment of the present invention. 
     S 108 , If the mobile phone A detects that the user A answers the second call, the second call is connected, and the first call is cut off or is in an on-hold state. 
     S 110 . If the mobile phone A detects that the user A cuts off the second call, that is, the second call initiated by the mobile phone C is rejected, the mobile phone A displays the first interface that shows that the mobile phone A is in a call with the mobile phone B. In this case, the mobile phone A continues outputting the call voice between the first terminal and the second terminal, stops outputting the prompt tone to stop prompting the call event, so as to eliminate interference caused by the prompt tone to the first call in a timely manner. The mobile phone A stops outputting the prompt tone by eliminating the prompt tone in the downlink signal. 
     After the mobile phone A detects an indication indicating that the user cuts off the second call, the display screen of the mobile phone A no longer displays the second interface, and returns to the first interface. 
     When detecting that the user A cuts off the second call, the mobile phone A may perform S 112  of determining whether the prompt tone disappears. If the prompt tone does not disappear, S 114  of eliminating the prompt tone is performed. Alternatively, when detecting that the user A cuts off the second call, the mobile phone A may not determine whether the prompt tone disappears, that is, does not perform S 112 , and directly performs S 114  of eliminating the prompt tone. 
     It may be understood that the mobile phone A constantly receives downlink signals sent by the network. Although prompt tones received by the mobile phone A may not be in a same downlink signal, prompt tones in a whole call process may be considered as a whole. For example, after receiving the second call, the mobile phone A outputs a sound, and the sound includes a prompt tone; and after the user A cuts off the second call, the mobile phone A eliminates the prompt tone. Herein, the prompt tone eliminated by the mobile phone A is a prompt tone detected after the user A cuts off the second call, instead of the prompt tone that has been output by the mobile phone A. Likewise, in this embodiment of the present invention, downlink signals in a process of the call between the mobile phone A and the mobile phone B may be considered as a whole. 
     Referring to  FIG.  3   , an embodiment of the present invention further provides another call prompt method, so as to resolve the foregoing problem in an existing CDMA communications network. After the mobile phone A receives the second call initiated by the mobile phone C to the mobile phone A in  FIG.  2    in S 104 , and the call prompt method provided in this embodiment of the present invention may further include the following steps. 
     S 206 . The mobile phone detects a prompt tone. 
     After receiving the second call, the mobile phone A detects, in real time, whether a received downlink signal includes a prompt tone. 
     S 208 . The mobile phone A determines whether the prompt tone disappears. 
     If the prompt, tone disappears before the user A selects whether to answer the second call, S 210  is performed; or if the prompt tone does not disappear before the user A selects to answer the second call, whether the call voice includes a prompt tone continues to be detected. 
     After the mobile phone C initiates a call to the mobile phone A, the mobile phone C may abandon the call to the mobile phone A. If the mobile phone C abandons the initiated call, the mobile phone C sends a call abandoning notification message to the network. After the mobile phone C abandons the call, the network no longer sends the prompt tone of the second call to the mobile phone A, That is, the downlink signal received by the mobile phone A includes the call voice between the mobile phone A and the mobile phone B, but no longer includes the prompt tone of the second call. In this case, the mobile phone A detects no prompt tone. If the mobile phone A detects no prompt tone in N prompt tone detection periods, it may be determined that the prompt tone disappears, where N is a positive integer. 
     S 210 . The mobile phone A displays the first interface, and continues outputting the call voice between the first terminal and the second terminal. The first interface shows that the first terminal is in a call with the second terminal. 
     If the mobile phone A detects that the prompt tone disappears, or detects no prompt tone, the mobile phone A may consider that the mobile phone C has stopped initiating the call to the mobile phone C. In this case, the mobile phone A may display the first interface showing that the mobile phone A is in a call with the mobile phone B, instead of the second interface of the call initiated by the mobile phone C. 
     The mobile phone A is still in a call with the mobile phone B, and the downlink signal received by the mobile phone A includes the call voice between the mobile phone A and the mobile phone B. After processing the downlink signal, the mobile phone A may continue outputting the call voice between the mobile phone A and the mobile phone B. 
     It may be understood that the mobile phone A constantly receives downlink signals sent by the network. Although call voices received by the mobile phone A may not be in a same downlink signal, call voices in a whole call process may be considered as a whole. 
     Referring to  FIG.  4    and  FIG.  5   , embodiments of the present invention provide prompt tone detection and elimination methods, so as to further describe the methods shown in  FIG.  2    and  FIG.  3   .  FIG.  4    is an implementation of the method shown in  FIG.  2   , and  FIG.  5    is an implementation of the method shown in  FIG.  3   . The mobile phone A may add a prompt tone detection module  330  and/or a prompt tone elimination module  340  following voice decoding. The prompt tone detection module  330  and the prompt tone elimination module  340  may be integrated into one module, or may be separate modules. Optionally, the prompt tone detection module  330  and the prompt tone elimination module  340  may be implemented by using a software algorithm. The prompt tone detection module  330  and the prompt tone elimination module  340  may be connected to the downlink call audio algorithm module  350  in series or in parallel. That is, after the PCM data is obtained by means of voice decoding, prompt tone detection may be first performed, and then processing based on a downlink call audio algorithm is performed. Alternatively, after the PCM data is obtained by means of voice decoding, prompt tone detection and processing based on a downlink call audio algorithm may be performed at the same time, so as to avoid or reduce a delay caused by the prompt tone detection to a downlink call in a normal voice state. The prompt tone elimination module  340  may also be integrated into a noise suppression NS module  360 . To some extent, when the mobile phone A is in a call state, the prompt tone of the second call may also be considered as noise. 
     Optionally, the mobile phone A may detect a prompt tone by using a linear spectrum detection method in signal processing. Because a fundamental frequency of a beep tone is a single-frequency tone that lasts for a time period and that has a constant amplitude and a constant frequency, a frequency of a beep tone may be detected based on a time-frequency characteristic of the beep tone. After the frequency corresponding to the beep tone is detected, the prompt tone beep may be eliminated by changing an amplitude value that is corresponding to the frequency and that is in an amplitude spectrum. 
     Specifically, the following linear spectrum detection method may be used for prompt tone detection. 
     (1). The mobile phone A may parse, according to the CDMA communications standard, a system broadcast message of a current cell to obtain network information, and obtains, according to the network information, prompt tone information pre-stored in the mobile terminal. The network information may include a home operator network and a network standard, or may include information about another network, for example, information about a base station. This is not limited in the present invention. The pre-stored prompt tone information is corresponding to the network information. The pre-stored prompt tone information includes a spectrum structure of a prompt tone, that is, frequency distribution or a frequency range of the prompt tone, and a signal strength or amplitude of the prompt tone, and may further include a time interval of the prompt tone, or the like. The mobile phone A may detect, according to the pre-stored prompt tone information, a prompt tone included in a downlink signal. Because there is a difference between the pre-stored prompt tone information and an actual prompt tone, the mobile phone A may also use the obtained pre-stored prompt tone information as prior information for detecting a prompt tone included in the downlink signal. It may be understood that the downlink signal on which whether a prompt tone is included is detected may be PCM data obtained after channel decoding and voice decoding are performed. 
     (2). After receiving a downlink signal sent by a base station, the mobile phone A first performs channel decoding, and then performs source decoding, so as to obtain the PCM data. 
     (3). The PCM data is divided into multiple overlapping data frames. For example, decoded PCM data may be divided into multiple data frames of 20 ms with an overlapping rate of 50%. A specific quantity of data frames is related to a volume of the PCM data, an overlapping rate, and a length of each data frame. It may be understood that 50% and 20 ms herein are merely used as examples for description, and specific data may be determined according to an actual condition, or may be determined according to an actual measurement condition. For example, an overlapping rate may range from 25% to 75%, and a length of a data frame may range from 10 ms to 30 ms. 
     (4). Each of the data frames is multiplied by a window function, and then a Fourier transformation is performed to obtain a complex spectrum. The window function may include a common data window such as a Hanning (harming) window, a Hamming (hamming) window, and a triangular window. This is not limited in the present invention. A signal may be truncated, by using the window function, to a limited time period for analysis. 
     (5). At each pre-estimated frequency, a correlation coefficient ρ between complex spectra of a previous frame and a current frame is calculated in a relaxation period, so as to obtain a correlation coefficient estimate. The relaxation period may be set and adjusted according to an actual condition, for example, the relaxation period may be a value between 40 ms and 60 ms. A specific value of the relaxation period is not limited in the present invention. 
     In calculation based on a mathematical formula, a calculation method for the correlation coefficient is 
               ρ   XY     =         Cov   ⁡   (     X   ,   Y     )           D   ⁡   (   X   )       ⁢       D   ⁡   (   Y   )           .           
Cov(X, Y) is a covariance, D(X) is a variance of X and D(Y) is a variance of Y. ρ XY  ∈[0,1], and a larger value of ρ XY  indicates a stronger correlation.
 
     Therefore, once Fourier coefficients of two adjacent data frames are obtained and substituted into the variables X and Y, a correlation coefficient between complex spectra of the two adjacent data frames may be obtained by means of calculation. 
     Each pre-estimated frequency may be a frequency obtained according to the pre-stored prompt tone information in (1), may be a frequency that is obtained by performing sampling according to a set frequency range after an actual prompt tone is analyzed, or may be a frequency determined by analyzing a spectrum characteristic of a call voice signal. This is not limited in this embodiment of the present invention. 
     (6). If the correlation coefficient exceeds a preset threshold, it is determined that there is an obvious single-frequency tone signal at the frequency, that is, a beep tone. In addition, an amplitude spectrum estimate of the frequency may be multiplied by the correlation coefficient estimate to obtain a frequency amplitude estimate of the beep tone. 
     Optionally, the prior information of the beep tone in (1) may be compared with the frequency amplitude estimate of the beep tone that is obtained according to the correlation coefficient estimate, so as to further improve detection accuracy. If the frequency of the beep tone that is obtained according to the correlation coefficient estimate is distributed at a frequency on which main energy in the prior information of the beep tone is distributed, it may be further determined that the beep tone is distributed at the frequency obtained according to the correlation coefficient estimate. 
     (7). Beep tone detection is performed in real time according to the foregoing method; and if no beep tone is detected in a preset quantity of consecutive time intervals in which a beep tone normally appears, it may be determined that the beep tone disappears. 
     (1) is an optional step, that is, the solution can be implemented even without (1). In this case, the frequency determined in step (5) may be a frequency obtained by sampling from a preset frequency range at a preset time interval, or may be a frequency obtained by sampling from a pre-estimated frequency range obtained by means of preliminary analysis according to a characteristic of the received downlink signal. 
     If specific information of the beep tone pre-stored in the mobile phone A in (1) completely matches information of the beep tone carried in the downlink signal, after the PCM data is obtained, the beep tone does not need to be detected by using the foregoing linear spectrum detection method. The mobile phone A may determine the beep tone by detecting, at a pre-stored frequency, whether an amplitude value corresponding to the downlink signal exceeds an amplitude threshold or is the same as or close to a pre-stored signal strength or amplitude. That at the pre-stored frequency, the amplitude value corresponding to the downlink signal is close to the preset signal strength means that a difference between the amplitude value corresponding to the downlink signal and the preset signal strength does not exceed a threshold. 
     It may be understood that various linear spectrum detection methods in the signal processing field may be adjusted and improved according to a characteristic of the prompt tone, and then be used to detect a prompt tone. A method for detecting a prompt tone is not limited to the foregoing algorithm. 
     It may be understood that the mobile phone A may be one or more processors. The call prompt method may be implemented by using a processor in the mobile phone A, or by using a processor, a necessary auxiliary circuit, and a necessary auxiliary device (such as a radio frequency chip and a display screen), or by using a chip or a chip-set formed by multiple chips. 
     According to the foregoing call processing method, a problem that an unconnected second call causes interference to a current call of the mobile phone A can be resolved without changing an existing network architecture or an existing network communications standard. This is simpler, more convenient, and more cost-effective when compared with a solution in which a network communications standard is changed and an operator&#39;s network device is updated. 
     Referring to  FIG.  6   , an embodiment of the present invention provides a terminal  400 , so as to implement the methods in  FIG.  2    and  FIG.  3   . All the solutions and features that can be implemented in  FIG.  2    and  FIG.  3    are applicable to this embodiment, and details are not described herein again. 
     Specifically, the terminal  400  may include: 
     a display module  402 , configured to display a first interface, where the first interface shows that the terminal is in a call with a second terminal, where 
     the display module  402  is further configured to display a second interface, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     an output module  404 , configured to output a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; and 
     a processing module  406 , configured to detect whether the call initiated by the third terminal to the terminal is rejected. 
     The processing module  406  is further configured to detect whether the third terminal stops initiating the call to the terminal. 
     The output module  404  is further configured to: when the processing module  406  detects that the call initiated by the third terminal to the terminal is rejected, continue outputting the call voice between the terminal and the second terminal, and stop outputting the prompt tone to stop prompting the call event; or when the processing module  406  detects that the third terminal stops initiating the call to the terminal, continue outputting the call voice between the first terminal and the second terminal. 
     The display module  402  is further configured to: when the processing module  406  detects that the third terminal stops initiating the call to the terminal, and the output module  404  continues outputting the call voice between the first terminal and the second terminal, stop displaying the second interface, and display the first interface. 
     The processing module  406  may be configured to detect the prompt tone. 
     Optionally, the processing module  406  determines, by detecting that the prompt tone disappears, that the third terminal stops initiating the call to the first terminal. For example, if the processing module detects no prompt tone in N prompt tone detection periods, it is determined that the prompt tone disappears, where N is a positive integer. 
     Optionally, the output module  404  may stop outputting the prompt tone by changing an amplitude value of a frequency corresponding to the prompt tone. 
     For a specific method used by the processing module  406  to detect a prompt tone, refer to related description of the methods in  FIG.  3    and  FIG.  4   , and details are not described herein again. 
     The terminal  400  may be configured to implement the call prompt methods in  FIG.  2    and  FIG.  3   , including the solutions in  FIG.  4    and  FIG.  5    that are further described for the call prompt methods in  FIG.  2    and  FIG.  3   . Therefore, all the solutions and features in the methods disclosed in the embodiments of the present invention are applicable to the terminal  400  shown in  FIG.  4   , and details are not described herein again. 
     Optionally, the display module  402  of the terminal  400  may be a display screen of the terminal, the processing module  406  may be a processor of the terminal, and the output module may be an audio frequency circuit of the terminal. This is not limited in the present invention. 
     The terminal  400  can resolve a problem that an unconnected second call causes interference to a current call without changing an existing network architecture or an existing network communications standard. This is simpler, more convenient, and more cost-effective when compared with a solution in which a network communications standard is changed and an operator&#39;s network device is updated. 
     Referring to  FIG.  7   , the present invention further provides a terminal  500  that implements the method provided in the embodiments of the present invention, so as to execute the foregoing call prompt call methods in  FIG.  2    and  FIG.  3   . 
       FIG.  7    shows a block diagram of a partial structure of a terminal  500  related to this embodiment of the present invention. Referring to  FIG.  7   , the terminal  500  includes components such as an RF (Radio Frequency, radio frequency) circuit  510 , a memory  520 , another input device  530 , a display screen  540 , a sensor  550 , an audio frequency circuit  560 , an I/O subsystem  570 , a processor  580 , and a power supply  590 . A person skilled in the art may understand that the structure of the mobile terminal shown in  FIG.  7    constitutes no limitation to the mobile terminal; that is, more or fewer components than those shown in the figure may be included, some components may be combined, or some components may be separated, or the components are arranged in a different way. 
     The following describes all constituent components of the terminal  500  in detail with reference to  FIG.  7   . 
     The RF circuit  510  may be configured to receive or send a signal in an information receiving or sending process or a call process; particularly, after receiving downlink information of a base station, send the downlink information to the processor  580  for processing; and send designed uplink data to the base station. Generally, the RF circuit  510  includes but is not limited to an antenna, at least one amplifier, a transceiver; a coupler, an LNA (Low Noise Amplifier, low noise amplifier), a duplexer, and the like. In addition, the RF circuit  510  may further communicate with a network and another device by means of wireless communications. The wireless communications uses a CDMA communications standard or protocol for communication, and may further use any one of the following communications standards or protocols, including but not limited to: GSM (Global System of Mobile communication, Global System for Mobile communications), GPRS (General Packet Radio Service, General Packet Radio Service), WCDMA (Wideband Code Division Multiple Access, Wideband Code Division Multiple Access), LTE (Long Term Evolution, Long Term Evolution), or the like. The CDMA communications standard is a telecom CDMA communications standard, including but not limited to CDMA IS-95, CDMA2000 1×, CDMA2000 2×, and CDMA2000 3×. 
     The memory  520  may be configured to store a software program and a module, and the processor  580  executes various functional applications of the terminal  500  and data processing by running the software program and the module stored in the memory  520 . The memory  520  may mainly include a program storage area and a data storage area. The program storage area may store an operating system, an application program (such as a sound playing function or an image playing function) that is required by at least one function, and the like. The data storage area may store data (such as audio data or a phonebook) that is created according to use of the terminal  500 , and the like. In addition, the memory  520  may include a high-speed random access memory, and may further include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or another volatile solid-state storage device. 
     The another input device  530  may be configured to receive numerical or character information that is input, and generate signal input related to user settings and function control of the terminal  500 . Specifically, the another input device  530  may include but not limited to one or more of: a physical keyboard, a function button (such as a volume control button or an on/off button), a trackball, a mouse, and a joystick, an optical mouse (the optical mouse is an extension to a touch-sensitive surface that does not display visual output, or an extension to a touch-sensitive surface formed by a touchscreen). The another input device  530  is connected to another input device controller  571  of the I/O subsystem  570 , and exchanges a signal with the processor  580  under control of the another input device controller  571 . 
     The display screen  540  may be configured to display information entered by a user or information provided for a user, and various menus on the terminal  500 , and may further receive user input. Specifically, the display screen  540  may include a display panel  541  and a touch panel  542 . The display panel  541  may be configured in a form of an LCD (Liquid Crystal Display, liquid crystal display), an OLED (Organic Light-Emitting Diode, organic light-emitting diode), or the like. The touch panel  542 , also referred to as a touchscreen or a touch-sensitive screen, can collect a contact or contactless operation performed by a user on or near the touch panel  542  (for example, an operation performed by the user on or near the touch panel  542  by using any appropriate object or accessory, such as a finger or a stylus, or a somatosensory operation may be included, where the operation includes operation types such as a single-point control operation and a multi-point control operation), and can drive a corresponding connection apparatus according to a preset program. Optionally, the touch panel  542  may include two parts: a touch detection apparatus and a touch controller. The touch detection apparatus detects a touch position and a touch gesture of the user, detects a signal brought by a touch operation, and transfers the signal to the touch controller. The touch controller receives touch information from the touch detection apparatus, converts the touch information into information that can be processed by the processor, and then sends the information to the processor  580 , and can receive and execute a command sent by the processor  580 . In addition, the touch panel  542  may be implemented by using multiple types such as a resistive type, a capacitive type, infrared, and a surface acoustic wave, or the touch panel  542  may be implemented by using any technology developed in the future. Further, the touch panel  542  may cover the display panel  541 , and a user may perform an operation on or near the touch panel  542  covered on the display panel  541  according to content displayed on the display panel  541  (the displayed content includes but is not limited to a soft keyboard, a virtual mouse, a virtual key, and an icon). After detecting the operation performed on or near the touch panel  542 , the touch panel  542  transfers the operation to the processor  580  by using the I/O subsystem  570 , so as to determine user input; and subsequently the processor  580  provides corresponding visual output on the display panel  541  by using the I/O subsystem  570  according to the user input. Although the touch panel  542  and the display panel  541  in  FIG.  7    are used as two independent components to implement input and input functions of the terminal  500 , in some embodiments, the touch panel  542  and the display panel  541  may be integrated to implement the input and output functions of the terminal  500 . 
     The terminal  500  may further include at least one type of sensor  550 , such as a light sensor, a motion sensor; or another sensor. Specifically, the light sensor may include an ambient light sensor and a proximity sensor. The ambient light sensor may adjust luminance of the display panel  541  according to brightness or dimness of ambient light. The proximity sensor may turn off the display panel  541  and/or backlight when the terminal  500  moves close to an ear. As a type of the motion sensor, an accelerometer sensor may detect an acceleration value in each direction (generally, three axes), and detect a value and a direction of gravity when the accelerometer sensor is still, and may be used in an application for recognizing a mobile terminal posture (such as screen switching between landscape and portrait modes, a related game, or magnetometer posture calibration), a function related to vibration recognition (such as a pedometer or a knock), and the like. For other sensors that may also be configured on the terminal  500 , such as a gyroscope, a barometer, a hygrometer, a thermometer, and an infrared sensor, details are not described herein. 
     The audio frequency circuit  560 , a speaker  561 , and a microphone  562  may provide an audio interface between a user and the terminal  500 . The audio frequency circuit  560  may transmit, to the speaker  561 , a signal converted from received audio data, and the speaker  561  converts the signal into a sound signal for output. In addition, the microphone  562  converts a collected sound signal into a signal; and after being received by the audio frequency circuit  560 , the signal is converted into audio data, and then the audio data is output to an RI; circuit  108  for sending to, for example, another mobile terminal, or the audio data is output to the memory  520  for further processing. 
     The I/O subsystem  570  is configured to control external input and output external devices, and may include another input device controller  571 , a sensor controller  572 , and a display controller  573 . Optionally, one or more other input control device controllers  571  receive a signal from the another input device  530  or send a signal to the another input device  530 . The another input device  530  may include a physical button (such as a press button or a rocker button), a dial, a slider switch, a joystick, a click wheel, an optical mouse (the optical mouse is an extension to a touch-sensitive surface that does not display visual output, or an extension to a touch-sensitive surface formed by a touchscreen). It should be noted that the another input control device controller  571  may be connected to any one or more of the foregoing devices. The display controller  573  in the I/O subsystem  570  receives a signal from the display screen  540  and/or sends a signal to the display screen  540 . After the display screen  540  detects user input, the display controller  573  converts the detected user input into interaction with a user interface object displayed on the display screen  540 , so as to implement man-machine interaction. The sensor controller  572  may receive a signal from one or more sensors  550  and/or send a signal to one or more sensors  550 . 
     As a control center of the terminal  500 , the processor  580  connects all parts of the entire mobile terminal by using various interfaces and lines, and performs various functions of the terminal  500  and data processing by running or executing the software program and/or the module that are/is stored in the memory  520  and by invoking data stored in the memory  520 , so as to perform overall monitoring on the mobile terminal. Optionally, the processor  580  may include one or more processing modules. Preferably, the processor  580  may integrate an application processor and a modem processor. The application processor mainly processes an operating system, a user interface; an application program, and the like, and the modem processor mainly processes wireless communications. It may be understood that the foregoing modem processor may be not integrated into the processor  580 . 
     The terminal  500  further includes the power supply  590  (for example, a battery) that supplies power to each component. Preferably, the power supply may be logically connected to the processor  580  by using a power supply management system, so as to implement functions such as management of charging, discharging, and power consumption by using the power supply management system. 
     Although not shown in the figure, the terminal  500  may further include a camera, a Bluetooth module, a Wireless Fidelity (Wireless-Fidelity, Wi-Fi or WiFi) module, and the like, which are not described herein. 
       FIG.  7    is a block diagram of a generic structure of a mobile terminal. It may be understood that different mobile terminals may include more or fewer structures than that in  FIG.  7   . For example, the mobile terminal may further include a structure such as a Bluetooth module, a Wi-Fi module, or an infrared module. 
     Specifically, 
     the RF circuit  510 , which may be referred to as a transceiver, may be configured to communicate with a network device; and 
     the processor  580  may invoke one or more programs stored in the memory  520 , so as to perform the following operations: 
     displaying a first interface on the display screen  540 , where the first interface shows that the terminal is in a call with a second terminal: 
     displaying a second interface on the display screen  540 , where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     outputting, on the terminal, a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; and 
     if the call initiated by the third terminal to the terminal is rejected, continuing outputting, on the terminal, the call voice between the terminal and the second terminal, and stopping outputting the prompt tone; and/or 
     if the third terminal stops initiating the call to the terminal, displaying the first interface on the display screen of the terminal, and continuing outputting, on the terminal, the call voice between the terminal and the second terminal. 
     For prompt tone detection and elimination methods, refer to description in the method embodiments, and details are not described herein again. 
     It may be understood that the processor may include multiple processor chips. For example, one processor chip processes prompt tone detection and/or elimination, and another processor chip processes another operation used for implementing the solution. An example is merely used for description herein, and all other solutions of similar principles belong to the scope of the embodiments of the present invention. 
     It should be noted that in a specific implementation process, a person skilled in the art should understand that in addition to the structure shown in  FIG.  7   , the terminal  500  further includes another device required for normal running. Furthermore, a person skilled in the art should understand that, according to a specific requirement, the terminal  500  may further include a hardware device that implements another additional function. In addition, a person skilled in the art should understand that the terminal  500  may also include only a device required for implementing this embodiment of the present invention, without a need of including all devices shown in  FIG.  7   . 
     The terminal  500  can resolve a problem that an unconnected second call causes interference to a current call of the terminal without changing an existing network architecture or an existing network communications protocol. This is simpler, more convenient, and more cost-effective when compared with a solution in which a network communications standard is changed and an operator&#39;s network device is updated. 
     It should be noted that the terminal that implements the call prompt method in this embodiment of the present invention may also be a processor, may be a processor, a necessary auxiliary circuit, and a necessary auxiliary device (such as a display screen and a speaker), or may be a chip or a chip-set formed by multiple chips. 
     An embodiment of the present invention further provides a processor, so as to implement the methods in  FIG.  2    and  FIG.  3    in the embodiments of the present invention. All the solutions and features that can be implemented in  FIG.  2    and  FIG.  3    are applicable to this embodiment, and details are not described herein again. 
     The processor may be configured to perform the following operations: 
     controlling to display a first interface, where the first interface shows that the terminal is in a call with a second terminal; 
     controlling to display a second interface, where the second interface prompts that a third terminal initiates a call to the terminal, and at this moment, the terminal is still in a call with the second terminal; 
     outputting a sound, where the sound includes a prompt tone and a call voice between the terminal and the second terminal, and the prompt tone is used to prompt that the third terminal initiates a call to the terminal; 
     if the call initiated by the third terminal to the terminal is rejected, continuing outputting the call voice between the terminal and the second terminal, and stopping outputting the prompt tone; and/or 
     if the third terminal stops initiating the call to the terminal, controlling to display the first interface, and continuing outputting, on the terminal, the call voice between the terminal and the second terminal. 
     It may be understood that the operations of the processor are described from a perspective of the processor. When displaying the first interface, the second interface, or the like, the processor needs to use at least the display screen to display information, and another necessary auxiliary circuit to transmit the information. The information includes but is not limited to data, a message, a value, a parameter, an instruction, or signaling. When outputting the sound or the like, the processor needs to use at least an audio frequency circuit to output voice information. When making a call, receiving the second call, or the like, the processor also needs to use a transceiver to interact with a network. However, if the processor integrates an RF circuit, that is, the processor integrates an AP function and a BP function, the processor may not use another modern (Modem), but still needs to control an antenna to send and receive signals. The processor may invoke program information stored in the processor to implement the method in the embodiments of the present invention, or the processor may use information stored in a memory to implement the method in the embodiments of the present invention. 
     Optionally, detection of the foregoing prompt tone may be implemented by the processor. To improve a processing speed, the processor may also control a DSP (Digital Signal Processor, digital signal processor) to detect the prompt tone. Then the processor performs corresponding processing according to a detection result of the DSP. Likewise, the processor may also control the DSP to eliminate the prompt tone. For specific prompt tone detection and elimination methods, refer to detailed description of the methods shown in  FIG.  2    and  FIG.  3   , and details are not described herein again. 
     It may be understood that the processor needs to use another auxiliary component to implement the call prompt solution in the embodiments of the present invention, and the another auxiliary component is controlled by the processor to assist in implementing the solution. Therefore, the call prompt method in the embodiments of the present invention may be considered to be directly implemented by the processor. 
     It should be understood that in the embodiment of the present invention, the processor may be a central processing unit (Central Processing Unit, “CPU” for short), or the processor may be another general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ARC), a field programmable gate array (FPGA), or another programmable logic device, discrete gate or transistor logic device, discrete hardware component, or the like. The general purpose processor may be a microprocessor, or may be any conventional processor or the like. 
     It should be noted that, in all the embodiments of this specification, the mobile terminal generally includes at least one processor (for example, a CPU), at least one transceiver, and at least one bus, as shown in  FIG.  7   . As a control center of the electronic device, the processor connects all parts of the entire electronic device by using various interfaces and lines, and performs various functions of the electronic device and/or data processing by running or executing a software program and/or a module stored in a storage unit and by invoking data stored in the storage unit. The processor may be formed by an integrated circuit (Integrated Circuit, IC for short), for example, may be formed by a singly-encapsulated IC, or may be formed by multiple connected encapsulated ICs with a same function or different functions. For example, the processor may include only a central processing unit (Central Processing Unit, CPU for short), or may be a combination of a GPU, a digital signal processor (Digital Signal Processor, DSP for short), and a control chip (such as a baseband chip) in a communications unit. In an implementation of the present invention, the CPU may be a single computing core, or may include multiple computing cores. 
     A hardware structure shown in  FIG.  7    and the foregoing description are applicable to various mobile terminals provided in the embodiments of the present invention. A person of ordinary skill in the art may understand that all or some of the steps of the foregoing methods may be implemented by a program instructing relevant hardware. The program may be stored in a computer readable storage medium. The storage medium includes: a ROM, a RAM, and an optical disc. 
     A person of ordinary skill in the art may be aware that, in combination with the examples described in the embodiments disclosed in this specification, units and algorithm steps may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on particular applications and design constraint conditions of the technical solutions. A person skilled in the art may use different methods to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of the present invention. 
     The foregoing descriptions are merely specific implementations of the present invention, but are not intended to limit the protection scope of the present invention. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.