Abstract:
A voice communication system for achieving a public switch telephone network (PSTN) communication and an internet communication is provided. The system comprises a host, a control device and a telephone. The invention features advantages of both the PSTN and the internet, and further covers the natural shortcomings of each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the invention 
         [0002]    The invention relates generally to voice communication systems, and more specifically to a voice communication system using a personal computer for achieving a public switch telephone network (PSTN) communication and an internet communication. 
         [0003]    2. Description of the Related Art 
         [0004]    The telephone is a very important communication tool that most people are comfortable with. Currently, telephones generally are divided into PSTN-based phones and telephones compliant with a voice over internet protocol (hereinafter described as “VOIP-based phones”). It will be a great convenience to using telephones if PSTN-based phones and VOIP-based phones are integrated. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of the above-mentioned problems, an object of the invention is to provide a voice communication system. 
         [0006]    Another object of the invention is to provide a communication control device for achieving a PSTN communication and an internet communication. 
         [0007]    In one embodiment, the voice communication system comprises: a host, for executing an operating system and an internet communication program to carry out the internet communication; a communication control device coupled to the host, for achieving the internet communication and the PSTN communication; and, a telephone coupled to the communication control device  130 , for placing or receiving VOIP-based calls or PSTN-based calls via the communication control device. 
         [0008]    In another embodiment, the host comprises: a processing module for performing data processing; a storage module coupled to the processing module for providing data access; a network control circuit coupled to the processing module and the internet for controlling sending and receiving network packets; and, an audio circuit coupled to the processing module for performing sending and receiving operations of audio data. 
         [0009]    In a further embodiment, the communication control device comprises: an interface circuit coupled to the host for providing a signal with a specified voltage level according to audio data generated by the host; a switching circuit coupled to the interface circuit, a PSTN interface and a telephone interface, for coupling the telephone interface with one of the interface circuit and the PSTN interface according to a switching signal generated by the host; a detecting circuit coupled to a telephone line located between the host and the PSTN interface for detecting the state of the PSTN line and outputting a detecting result to the host; a filter coupled to a telephone line located between the audio circuit and the telephone interface. 
         [0010]    Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0012]      FIG. 1  shows a block diagram of a voice communication system according to a first embodiment of the invention. 
           [0013]      FIG. 2  shows a detailed diagram of a portion of the first embodiment. 
           [0014]      FIG. 3  shows a detailed diagram of the subscriber line interface circuit. 
           [0015]      FIG. 4A  is a flow chart illustrating a voice communication method according to the invention. 
           [0016]      FIG. 4B  is a flow chart illustrating a step of analyzing and communicating of  FIG. 4A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    The voice communication system of the invention will be described with reference to the accompanying drawings. 
         [0018]      FIG. 1  shows a block diagram of a voice communication system according to a first embodiment of the invention. Referring to  FIG. 1 , a voice communication system  100  according to the invention includes: a host  110 , for establishing an internet communication, wherein the host could be a desktop computer, a notebook, a tablet personal computer (PC), a personal digital assistant and a cellular phone; a communication control device  130 , for achieving the internet communication and the PSTN communication, wherein the communication control device  130  could be built inside the host  110 , or be a external device to the host  110 ; a telephone  150  coupled to the communication control device  130 , for placing or receiving VOIP-based calls or PSTN-based calls. In an alternative embodiment of the invention, the host  110  further comprises a housing (not shown) and the communication control device  130  is set in the housing. 
         [0019]    Referring also to  FIG. 1 , the host  110  includes a processing module  112  for performing data processing, wherein the processing module  112  includes a processor and a chipset (not shown) (comprising a south-bridge chip and a north-bridge chip (a south-bridge  210  shown in FIG.  2 )), and wherein the implementation of the processor and the chipset is well known to those skilled in the art and therefore will not be described herein; a storage module  114  coupled to the processing module for providing data access, wherein the storage module  114  according to this embodiment includes a nonvolatile storage unit (such as hard disk) and a volatile storage unit (such as a dynamic random access memory) (not shown), and wherein the implementation of the storage module  114  is also well known to those skilled in the art and thus will not be described herein; a network control circuit  118  coupled to the processing module  112  and the internet, for controlling sending and receiving network packets, wherein the storage module  114  could be a stand-along network interface card, or a network chip integrated into the chipset embedded in the processing module  112 , and wherein the implementation of the network control circuit  118  is also well known to those skilled in the art and thus will not be described herein; an audio codec  116  coupled to the processing module  112 , for performing sending and receiving operations of audio data, wherein the audio codec  116  could be a stand-along audio card, or an audio chip integrated into the chipset embedded in the processing module  112 . In the first embodiment, the storage module  114 , the network control circuit  118  and the audio codec  116  are coupled to the chipset (not shown) in the processing module  112 . Besides, the network control circuit  118  and the audio codec  116  are integrated into the chipset. Further, the host  110  has a network interface (such as a RJ-45 interface) (not shown) through which the network control circuit  118  is coupled to an internet line. 
         [0020]      FIG. 2  shows a detailed diagram of a portion of the first embodiment. As shown in  FIG. 2 , the communication control device  130  of this embodiment includes: a high-pass filter  260  for filtering low-frequency signals that the telephone  150  transmits and generating a first differential signal; a subscriber line interface circuit (SLIC)  230  for providing a third differential signal with a specified voltage level according to a first control signal and a second differential signal output from the audio codec  116 ; a detector  250  for detecting the state of a PSTN line  280  and generating a detecting signal; a switch  240  for connecting the telephone  150  with the internet via the host  110 , or coupling the telephone  150  with the PSTN line  280  according to a second control signal output from the audio codec  116 ; two RJ-11 interfaces  281 ,  282  coupled to the telephone  150  and the PSTN line  280  respectively. 
         [0021]    Referring also to  FIG. 2 , two RJ-11 interfaces  281 ,  282  of the host  110  are coupled to the telephone  150  and the PSTN line  280  respectively. And, the high-pass filter  260 , coupled to a telephone line (consisting of a tip wire and a ring wire) located between the interface  281  and the switch  240 , filters low-frequency ring signals and generates a first differential signal. The detector  250  detects the state of the PSTN line  280 , e.g., the voltage variations on the PSTN line  280 , to generate a detecting signal. There are three typical states on the conventional PSTN line  280 . They are an on-hook state, an off-hook and a ring state. The voltages on the PSTN line  280  vary with different states. Since the states and the variations on the PSTN line  280  are well known, the description is omitted herein. The first terminal of the switch  240  is connected to the telephone  150  and the high-pass filter  260  and its second terminal receives the third differential signal, with its third terminal connected to the PSTN line  280 . According to the second control signal, the switch  240  couples the telephone  150  with the internet via the host  110 , or with the PSTN line  280 . 
         [0022]    Referring also to  FIG. 2 , both of the south-bridge chip  210  and the audio codec  116  are mounted on a motherboard (such as a computer motherboard) in this embodiment. An analog-to digital converter  221  embedded in the audio codec  116  receives and converts the first differential signal into a first digital signal. In general, the first digital signal includes voice data and/or keypress data. With respect to voice data, they are sent from a control unit  223  (e.g., a DSP, a MPU or a logic circuit etc.) to the south-bridge chip  210  via a high definition audio interface, and then processed using the hardware and the software of the host  110 . For example, while transmitted via the internet to a remote device, the voice data will be first processed using a VOIP-compliant program (such as a SKYPE program) which resides in and is executed on the host  110 , and then be delivered to the remote device via the internet. On the contrary, while receiving the voice data from the remote device via the internet, the host  110  processes the voice data using the VOIP-compliant program and then transmits the voice data to the audio codec  116  via the south-bridge chip  210  and the high definition audio interface. Next, the audio codec  116  receives a second digital signal and then a digital-to-analog converter  222  converts the second digital signal into the analog second differential signal for output to the subscriber line interface circuit  230 . Meanwhile, the control unit  223  outputs a first control signal to the subscriber line interface circuit  230  for causing the subscriber line interface circuit  230  to generate a third differential signal responsive to the second differential signal. 
         [0023]    As previously described, the operating voltages of the motherboard and the telephone are generally different, i.e., the voltage level of signals transmitted on the motherboard different from the voltage level of signals transmitted by the telephone. The operating voltage of the motherboard is about 3-5V, whereas the operating voltage of the telephone is about (−5)-(−50)V. Therefore, the subscriber line interface circuit  230  mainly performs conversions between two different operating voltages. In this embodiment, the subscriber line interface circuit  230  converts the reference voltage V ref  into different DC voltage levels so as to convert the second differential signal into the third differential signal compliant with the telephone signaling form after receiving the enabled first control signal. Subsequently, the switch  240  receives and then outputs the third differential signal to the telephone  150  via the interface  281 . 
         [0024]    On the other hand, if the first digital signal contains the keypress data generated by using the telephone  150 , the control unit  223  decodes the first digital signal to obtain the keypress data according to a dual tone multiple frequency telephone signaling standard. In the case where the keypress data are a telephone number that a user dials to place an outgoing phone call, the control unit  223  transmits the telephone number to the host  110  so that the host  110  processes this telephone number using a VOIP-compliant program (such as SKYPE program). In addition, the control unit  223  can accordingly emulate a dial tone, a dialing keypad tone, a ring tone or a busy tone, and then return it to the telephone  150  through the digital-to-analog converter  222 , the subscriber line interface circuit  230 , the switch  240  and the interface  281 . Furthermore, the user is allowed to remotely control the VOIP-compliant program from the keypad on the telephone handset if the above-mentioned keypress data correspond to a predetermined data, e.g., the keypress data equal to “##”. For example, numeral keys “2”, “8”, “4”, “6”, “5 or #” on the keypad are employed to remotely control the cursor on the operating interface of the VOIP-compliant program for different directions and operations, such as “↑”, “↓”, “←”, “→” and “enter”. For the case where the keypress data correspond to another predetermined data, e.g., the keypress data equal to “**”, the control unit  223  outputs the second control data to configure the switch  240  via GPIO 3  to perform a mode switch between the internet and the PSTN line, i.e., the switch  240  being configured to couple the telephone  150  with either the PSTN line  280  or the subscriber line interface circuit  230 . 
         [0025]      FIG. 3  shows a detailed diagram of the subscriber line interface circuit. Recall that the subscriber line interface circuit  230  mainly performs conversions between two different operating voltages. Referring to  FIG. 3 , the subscriber line interface circuit (SLIC)  230  includes a SLIC controller  331  and a DC-to-DC converter  332 . The DC-to-DC converter  332  converts the reference voltage level V ref  into another DC voltage level V BAT  which is adapted to generate the DC voltage level of two signals Tip, Ring on the PSTN line. The DC voltage level is about (−5)-(−50)V. According to this embodiment, the reference voltage V ref  is about 12V and the DC voltage level V BAT  is about −90V. The audio codec  116  controls the SLIC controller  331  using the first control signal. If the first control signal is enabled, the SLIC controller  331  converts the second differential signal into a signal compliant with a telephone signaling form using the DC voltage level V BAT  provided by the DC-to-DC converter  332 . 
         [0026]    Referring now to  FIG. 1  and  FIG. 2 , in an alternative embodiment of the invention, the audio codec  116  doesn&#39;t analyze and process the first differential signal, but passes the data contained in the first differential signal to both the hardware and the software of the host  110  for processing via the south-bridge chip  210 . For example, the host  110  analyzes the data contained in the first differential signal using at least a pre-loaded program (such as a VOIP-compliant program, or a software program capable of performing an analysis according to a dual tone multiple frequency signaling standard). If the analysis indicates that the data contained in the first differential signal are voice data intended for a remote device, the host  110  will send the data contained in the first differential signal to the remote device via the south-bridge chip  210 , the network control circuit  118  and the internet. However, if the analysis indicates that the data contained in the first differential signal are keypress data, the host  110  will place a VOIP-based phone call according to the keypress data, or return signals to the communication control device  130 . 
         [0027]      FIG. 4A  is a flow chart illustrating a voice communication method according to the invention. In accordance with  FIGS. 1 ,  2  and  4 A, the voice communication method is detailed as follows. 
         [0028]    Step S 410 : Determine if the host  110  is on the internet. If “YES” and the PSTN line has been in a on-hook state for a pre-determined period, the connection between the telephone  150  and the internet is thereafter initiated and the flow goes to the step S 420 ; if “NO”, the flow goes to the step S 450 . Note that other pre-determined conditions could be included to accordingly determine whether the connection between the telephone  150  and the internet needs to be initiated or not in an alternative embodiment of the step S 410 . 
         [0029]    Step S 420 : Determine which state the PSTN line  280  is in. If the telephone handset is lifted, the flow advances to the step S 430  with respect to the detecting signal generated by the detector  250 . On the other hand, if there is an incoming PSTN-based phone call, the flow goes to the step S 440 . Apart from two above-mentioned conditions, the flow returns to the step S 420  repeatedly if the host  110  maintains communication with the internet. In this embodiment, the step S 420  may also determine if the host  110  is disconnected from the internet. If so, the flow returns to the step S 410 . 
         [0030]    Step S 430 : An analysis of keypress data is performed and the communication is in progress. Then, the flow returns to the step S 420 . 
         [0031]    Step S 440 : If the telephone  150  is on hook (i.e. the handset in the cradle), the control unit  223  generates a second digital signal with a ring tone and then the digital-to-analog converter  222  converts the second digital signal into an analog second differential signal. Next, the SLIC  230  converts the second differential signal into the third the differential signal compliant with the telephone signaling form. Finally, the third differential signal rings the bell in the telephone  150  via the switch  240 . On the other hand, if the telephone  150  is in use, i.e., off hook, the operations of the step S 440  will be performed as follows. The control unit  223  generates a second digital signal with a notifying tone and then the digital-to-analog converter  222  converts the second digital signal into an analog second differential signal. Next, the SLIC  230  converts the second differential signal into the third differential signal compliant with the telephone signaling form. Finally, the third differential signal is applied to the handset (the loudspeaker) in the telephone  150  via the switch  240  so as to notify the user of the incoming call. Then, the flow returns to the step S 420 . 
         [0032]    Step S 450 : Establish or maintain the connection between the telephone  150  and the PSTN line  280  if the host  110  is not on the internet. Then, the flow returns to the step S 410 . In this step, while the telephone  150  attempts to connect with the PSTN line  280 , the control unit  223  is employed to invert the second control signal and then transmit the inverted second control signal to the switch  240  via GPIO 3  so as to control the connection between the telephone  150  and the PSTN line  280 . 
         [0033]      FIG. 4B  is a flow chart illustrating a step of analyzing and communicating of  FIG. 4A . In accordance with  FIGS. 1 ,  2 ,  4 A and  4 B, the step S 430  of analyzing and communicating is detailed as follows. 
         [0034]    Step S 431 : First, the analog-to-digital  221  converts the analog first differential signal into the first digital signal. Next, according to a telephone signaling standard, the control unit  223  decodes the first digital signal and then analyzes what the first digital signal contains. If the first digital signal contains a first predetermined data, such as “##”, the flow will go to the step S 432 . If the first digital signal contains a second predetermined data, such as “**”, the flow will go to the step S 450 . This often occurs when the user is notified of an incoming PSTN-based phone call and then makes a mode switch to the PSTN for answering. Otherwise, the flow will go to step S 433 . In an alternative embodiment, more. conditions can be added in the step S 431  and a corresponding operation is thus performed if the first digital signal satisfies one of the conditions. 
         [0035]    Step S 432 : If the keypress data contained in first digital signal are “##”, it indicates that the user attempts to remotely control the operating interface of the VOIP-compliant program using the keypad on the telephone handset. For example, the user employs the numeral keys “2”, “8”, “4”, “6”, “5 or #” on the keypad to remotely control the cursor on the operating interface of the VOIP-compliant program for different directions and operations, like “↑”, “↓”, “←”, “→” and “enter”. Afterward, the control unit  223  sends the subsequent keypress data representing different directions via the south-bridge chip  210  to the host  110 . Accordingly, the host  110  processes the keypress data using the VOIP-compliant program. Then, the flow advances to the step S 433 . 
         [0036]    Step S 433 : If the keypress data contained in first digital signal are a telephone number, the telephone number will be provided to the host  110  via the south-bridge chip  210 . Thereafter, the host  110  places an outgoing VOIP-based phone call using the VOIP-compliant program in an internet-to-PSTN mode (such as SKYPE OUT). Likewise, if the keypress data contained in first digital signal represent one of VOIP phone users, the keypress data will be provided to the host  110  via the south-bridge chip  210 . The host  110  then places an outgoing VOIP-based phone call using the VOIP-compliant program in an internet-to-internet mode (i.e. a peer-to-peer mode). Further, after communication is initiated, the voice data contained in the first digital signal are sent to the internet via the VOIP-compliant program that is executed on the host  110 . On the other hand, the voice data from the internet are provided to the telephone  150  via the communication control circuit  130  by the host  110  using the VOIP-compliant program. Note that the flow returns to the step S 420  after the analysis and/or communication is terminated in this step. 
         [0037]      FIGS. 4A and 4B  disclosed above are illustrative only, as each step can be modified or combined with other steps without departing from the spirit of the invention. 
         [0038]    While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention should not be limited to the specific construction and arrangement shown and described, since various other modifications may occur to those ordinarily skilled in the art.