METHOD FOR SAVING A CALL

Abstract: The present publication describes a method for recording calls, wherein a first recording system (16) in an operator's system, which records information transmitted over a telephone connection, is controlled on the basis of tone frequency signals received from the calling subscriber connection (10). The publication also describes a method for recording calls, wherein a first recording system (16) or a second recording system in the operator's system, which records information transmitted over a telephone connection, on the basis of tone frequency signals received from the receiving subscriber connection (10). The invention is based on routing received calls via the recording system (16) by means of triggering action at the receiving end, and routing made calls on the basis of the duration of an off-hook signal received from the calling subscriber connection (10) to the recording system (16) and the receiving subscriber connection (14).

Description: METHOD FOR SAVING A CALL The invention relates to a method according to the preamble of claim 1 for recording calls under the control of a calling subscriber connection, wherein a first recording system located in the operator's system and recording data transmitted over a telephone connection is controlled on the basis of a tone frequency dialling received from the calling subscriber connection. The invention also concerns a method according to the preamble of claim 7 for recording calls under the control of a receiving subscriber connection, wherein a first recording system or a second recording system located in the operator's system and recording data transmitted over a telephone connection is controlled on the basis of a tone frequency dialling received from the receiving subscriber connection. According to the prior art, in a situation where a receiving telephone subscriber wants to record a call in an operator's system, the receiving subscriber must give the calling subscriber the number of the service center which provides the call recording service as its own telephone number information. The service center records the call routed over it and routes the call to the receiving subscriber connection. In a situation where the calling subscriber wants to record a call in the operator' s system, he calls the service center/server and notifies it of the desired receiving subscriber number. Thereafter the service center connects the call to the desired receiving subscriber number. Such an arrangement has been implemented in the MCC "Call Recording" system by Merling Systems. It is also possible for telephone subscribers to record calls or parts thereof by using devices of their own connected to the subscriber line. A deficiency hampering the prior art solutions in a recording service implemented in the operator's system lies in that the telephone subscriber must know in advance whether he wants to record a received or made call. When wishing to record a call or a part thereof, the calling subscriber must first call a customer-specific telephone number in the recording system and feed in a required password by using tone frequency dialling, whereafter he needs to supply the receiving subscriber number. If, then, the receiving subscriber wants to record a call or a part thereof, the calling subscriber must call a number in the recording system in order to enable the routing of the telephone connection to the receiving subscriber connection via the recording system. What is particularly problematic here is that the calling subscriber must perform extra measures to enable a service offered to the receiving subscriber. The receiving subscriber may distribute the recording center number as its own telephone number, whereby a calling subscriber setting up communication with the receiving subscriber is spared the extra trouble for a while. In practice, however, changing telephone numbers causes extra inconvenience to all those having been calling the receiving subscriber prior to the phone number swap, and who conduct conversations with the receiving subscriber that the latter wants to record. In addition, when the receiving subscriber wishes to stop using the recording service, the recording system number used must be unnecessarily reserved for call transfers to the normal number of the receiving subscriber connection, and load is thus imposed on the telephone network due to an extra call transfer operation, or else, the subscribers calling the receiving subscriber are again caused extra inconvenience due to the changed telephone number. Devices connected to a subscriber's PSTN subscriber connection are hampered by the drawback that separate installation of the recording equipment to each subscriber connection is required, which causes extra costs and trouble. The subscriber has to see to the maintenance of the recording equipment and arrange the space required by the recording equipment. The present invention aims at achieving an entirely novel type of method for recording calls, said method providing a solution to all the above-cited problems hampering the prior art. In the case of received calls the invention is based on routing all received calls to a recording server and starting call recording and controlling call recording by means of tone frequency dialling. As regards made calls, the invention is based on establishing a telephone connection to the receiving subscriber and the recording server, if an off-hook signal of certain duration is received from the calling subscriber. In more detail the method according to the invention for recording calls under the control of a calling subscriber is characterized by what is stated in the characterizing part of claim The method according to the invention for recording calls under the control of a receiving subscriber is further characterized by what is stated in the characterizing part of claim 7. The invention provides considerable benefits. In connection with establishing a connection or during the call the telephone subscriber may decide whether he wants to record the call received or made or a part thereof in the operator's system. Furthermore, the calling subscriber need not use any extra telephone numbers in addition to the receiving subscriber' s normal telephone number in order to enable recording or partial recording for the calling subscriber and/or the receiving subscriber. The fact that the subscriber receiving a call is provided the opportunity to record the call or a part thereof does not require any measures of the calling subscriber other than what is normally required when ordering a call. The subscription holder need not take care of the maintenance of the recording system, nor arrange the space required by the recording system. In the following, the invention is examined in more detail with reference to working examples in accordance with the annexed Figures. Figure 1 represents a system according to the invention for recording calls, whereby signals such as speech transmitted over a telephone connection are recorded under the control of the calling subscriber connection 10. Figure 2 is an operational diagram of a method according to the invention for recording calls, wherein signals such as speech transmitted over a telephone connection are recorded under the control of the receiving subscriber connection 14. Figure 3 is an operational diagram of a method according to the invention for listening to recorded calls, wherein a telephone subscriber is offered the possibility to listen to calls recorded for him or to parts thereof by means of a recording system 16. Figure 4 is a block diagram of a method according to the invention for using the recording system from a subscriber connection other than one connected to the recording system 16 by means of a hotline connection. Figure 5 is a block diagram of a method according to the invention for establishing a connection to the recording system by means of hotline and for recording signals transmitted over a telephone connection. In the examples illustrated in the Figures the terms calling subscriber connection 10 and receiving subscriber connection 14 refer to subscriptions to a public switched telephone network (PSTN) or a private telephone network. The non-recording party may also be a subscriber to a public land mobile network (PLMN) or a private mobile network. The term recording system 16 refers to a device or equipment connected to a telephone network, capable of recording and playing back sound transmitted over a telephone connection. In accordance with Figure 1, the following measures are taken when recording signals transmitted over a telephone connection under the control of a calling subscriber 10. A hotline or delayed hotline service is at the disposal of the calling subscriber 10 for establishing a telephone connection to the recording system 16. A hotline service is a service which is requested as soon as the subscriber lifts the receiver. From the point of view of the telephone exchange the hotline service is activated as soon as an off-hook signal of certain duration is received from the calling subscriber 10. Steps 101 - 103 are carried out to connect the call to the recording system 16 and to set the recording system 16 ready for operation: 101) An off-hook signal which has lasted for a given time is received from the calling subscriber connection 10 at the local exchange 25 at the calling end, the signal having been set as a request to set up a hotline or a delayed hotline connection at the local exchange 25. 102) The SCP 15 controlling the recording system 16 is routed the information that a hotline or a delayed hotline call is being established from the calling subscriber connection 10. The routing is carried out directly from the local exchange 25 at the calling end (102a) if it is at SSP level, otherwise the routing is carried out hierarchically from the nearest SSP-level exchange 26 (102b). 103) The call is connected to the recording service defined for the calling subscriber connection in the recording system 16 under the control of the SCP 15. The call is connected by means of a hotline or delayed hotline function at the local exchange 25 at the calling end, if the exchange is at SSP level, otherwise hierarchically at the nearest SSP exchange 26. Steps 104 to 105 are carried out for connecting a call to a receiving subscriber 14 such that the signals transmitted over the telephone connection established between the calling subscriber 10 and the receiving subscriber 14 can be recorded by means of the recording system 16: 104) A number dialling addressed to the usual number of the receiving subscriber connection is received from the calling subscriber connection 10. 105) The call is connected to the receiving subscriber connection 14, whereby a telephone connection between three subscriber lines is set up between the calling subscriber connection 10, the recording system 16 and the receiving subscriber connection 14. The connection to the receiving subscriber connection 14 may be established by means of the facility of the telephone network implemented when establishing telephone connections between three subscriber connections e.g. for the purpose of group calls. An arrangement is applied where the recording system 16 may express its state to a calling subscriber connection 10 e.g. by means of an audio message mixed into the telephone channel. During the call, tone frequency signals are received from the calling subscriber connection 10 and the recording system 16 is controlled by means of these tone frequency signals. A given tone frequency signal, such as "1 ", may be used to start recording the call, and some other or the same tone frequency signal may be used to end the recording. The tone frequency signals are received at the SCP 15 and the recording system 16 is controlled on the basis thereof. The first number 22 in the recording system is the number which routes the call to a recording service defined for a specific telephone subscriber in the recording system. The following measures are taken when recording signals transmitted over a telephone connection under the control of a receiving subscriber 12 in accordance with Figure 2. Step 201 is carried out prior to using the recording system for the first time when receiving calls at the receiving subscriber connection 14. Even then, this step is only necessary when the local exchange 21 at the receiving end is below SSP level, i.e. intelligent network (IN) techniques cannot be applied. Steps 202 to 204 are carried out for connecting the call to the recording system 16 and for setting the recording system 16 ready for use. The call is connected to a client-specific subscriber connection in the recording system 16, the first number 22 having been defined as the telephone number thereof. 201) Setting the auxiliary number 29 as the telephone number of the receiving subscriber connection 14 whose number has so far been the usual number 28. This is performed at the local exchange 21 at the receiving end by setting the auxiliary number 29 either alongside with the usual number 28, or to replace the usual number 28. 202) Receiving at the local exchange 21 at the receiving end a dialling for the usual number 28 from the direction of the calling subscriber connection 10. 203) Transmitting to the SCP 15 controlling the recording system information about the call being established. 204) When the local exchange 21 at the receiving end is at SSP level, the call is connected directly to the recording system 16 at a subscriber-specific connection thereof by means of a triggering action at the receiving end e.g. by means of a TDP12 element. If the local exchange 21 at the receiving end is below SSP level, a call transfer to the first number 22 is applied and the call is connected to a subscriber-specific connection according to the recording system 16. In a case where the connection to the recording system 16 is established by a call transfer, the first number 22 in the recording system has an auxiliary number 29 of the receiving subscriber connection 14 linked to it. The link is recorded such that it is accessible for the recording system 16 or the element, SCP 15, controlling the recording system. In a case where the connection to the recording system 16 is formed by a triggering action at the receiving end, the call can be connected to the receiving subscriber connection 10 on the basis of a dialling from the direction of the calling subscriber connection. Step 205 is carried out for connecting a call to a receiving subscriber connection 14 such that the signal transmitted over the telephone connection between the calling subscriber connection 10 and the receiving subscriber connection 14 can be recorded by means of the recording system 16: 205) Setting up a telephone connection to the auxiliary number 29 or the usual number 28 of the receiving subscriber connection. The connection can be established to the usual number 28 if the number has not been used for call transfer to the recording system during step 204. The information travelling between the calling subscriber connection 10 and the receiving subscriber connection 14 is routed via the recording system 16. The connection to the receiving subscriber connection 14 can be set up by means of a coπesponding facility which is in use when setting up group calls between three subscriber connections. An arrangement is used where the recording system 16 may express its state to the receiving subscriber connection 14 e.g. by means of an audio message mixed into the speech transmission channel. During the call tone frequency signals are received from the receiving subscriber connection 14 and the recording system 16 is controlled on the basis of tone frequency signals. A given tone frequency signal, such as "1", may be used to start recording a call and some other or the same tone frequency signal may be used to end the recording. The tone frequency signals are received at the SCP 15 and the recording system 16 is controlled on the basis thereof. Figure 3 is an operational diagram of a method for listening to recorded calls, wherein the following measures are taken. In steps 301 and 302 a signal indicating desire to listen to recorded calls is received and the recording system is set into the mode for playing back recorded calls. 301) A signal 18 indicating desire to listen to recorded calls, such as the audio frequency signal "#" is received from the calling subscriber connection 10 or any subscriber connection defined by means of a hotline service to be connected to the recording system. In the following, the subscriber connection from which the signal 18 has been received is referred to as the controlling subscriber connection 20. 302) The signal 18 is routed to the SCP 15 which controls the recording system 16 to the service menu, to the recording playback mode. In steps 303 and 304 the recording system 16 is controlled by means of tone frequency signals received from the subscriber connection and the sound or other information produced or played back by the recording system 16 is transmitted further. Steps 303 and 304 can be repeated a desired number of times one after the other. An IVR-type arrangement is used where the recording system 16 may indicate its state to the controlling subscriber connection 20 e.g. by means of an audio message mixed into the speech transmission channel. 303) During a call, tone frequency signals are received from the controlling subscriber connection 20 and the recording system 16 is controlled such that it performs various functions on the basis of the tone frequency signals. The recording system 16 may for example be controlled to play back, save or delete from memory a specific call or part of a call, or to move to a desired point in a played back and/or saved call recording by means of a rewind-type facility or a facility which in some other way defines a given point in a recorded call. The recording system 16 may also provide and/or repeat information which helps in controlling the recording system 16. This may take place in response to control signals received from the controlling subscriber connection 20. 304) Transmitting to the controlling subscriber connection 20 the signal repeated and/or produced by means of the recording system 16 on the basis of the routing in step 303 or otherwise. 305) Releasing the connection. Figure 4 illustrates in the form of a block diagram an example of a method according to the invention for using the recording system from a subscriber connection other than one connected via a hotline service. The term external subscriber connection 27 used in the example refers to any PSTN or PLMN subscriber connection which tries to contact the recording service number 19 of the recording system 16. The recording service number 19 may be the first number 22 with which communication was set up from the local exchange 21 at the receiving end in the example of Figure 2, or some other telephone number which connects to the recording system 16. The following measures are taken in the method according to Figure 4: 401) "Call to service" means that a dialling for the recording service number 19 is received from an external subscriber connection 27 from any PSTN or PLMN subscriber connection, or a dialling furnished with a calling subscriber identity in accordance with the external subscriber connection 27. 402) "Identification code inquiry" means that a tone frequency signal or tone frequency signals are received at the SCP controlling the recording system 16 from the calling subscriber connection 27 or under a calling subscriber connection identity in accordance with the external subscriber connection 27. 403) "OK" means that a telephone connection is established to the recording service number 19 and the received tone frequency signals are compared with the definition of acceptable tone frequency signals linked to the recording service number 19, i.e. the acceptable password. The comparison takes place at the SCP 15 or under the control of the SCP 15. 404) In response to received tone frequency signals communication with the recording service number 19 may be disconnected. This may happen if the tone frequency signals received differ from the acceptable ones. When the received tone frequency signals differ from those acceptable, a limited number of opportunities for supplying the acceptable tone frequency signal or signals may be offered. When a large enough number of unacceptable tone frequency signals has been received, the telephone connection to the recording service number 19 is cut off. 405) "Service active" means that the recording service 19 is enabled in response to received acceptable tone frequency signals. The default value is dialling the target number, i.e. if a number dialling was received, a telephone connection would be connected towards the subscriber connection according to the received dialling. 406) "#" means that a tone frequency signal such as "#" indicating desire to listen to recorded calls is received. 407) "Shift to main menu" means that in response to a received tone frequency signal indicating desire to listen, the recording system 16 is controlled to a mode for preparedness for listening to recorded calls by means of the SCP. 408) "3" means that a tone frequency dialling such as "3" is received, on the basis of which the recording system 16 is controlled to repeat recordings. 409) "Call released" means that telephone communication is disconnected when a signal indicating desire to disconnect communication is received. Figure 5 is a block diagram of a method according to the invention for setting up a connection to the recording system 16 by means of hotline and for recording signals transmitted over a telephone connection. The following measures are taken in the method according to Figure 5: 501) "Receiver off hook" means that an off-hook signal of certain length from the calling subscriber connection 10 is received at the telephone exchange which connects the hotline service. 502) "Dialling" means that it is determined on the basis of an off-hook signal received from the calling subscriber connection 10 whether the hotline service or delayed hotline service is connected. When an immediate hotline service is in use, the call is connected to the recording system 16 as soon as an off-hook signal has been received. When a delayed hotline service is used, the call is connected to the recording system 16 only when the duration of the off-hook signal has exceeded a given threshold value. If a number dialling is received from the subscriber connection 10 before the duration of the off-hook signal has exceeded the given threshold value the call is not connected to the recording system 16 in the case of a delayed hotline connection. 503) "Normal establishment of connection" means that when the duration of the off-hook signal before receiving a number dialling is shorter than the given threshold value, a normal telephone connection is established on the basis of the number dialling received without connecting the recording system 16 to the telephone connection by means of the hotline service. 504) "Dialling hotline service target number" means that the number of the receiving subscriber connection 14 is received from the calling subscriber connection 10 and a telephone connection is established to the receiving subscriber connection 14 such that a telephone connection between three subscriber connections is set up between the calling subscriber connection 10, the receiving subscriber connection 14 and the recording system 16. This may be carried out by using the facility of the telephone network used for group calls. 505) "Call connected" means that a call between three subscriber connections may be connected for a desired time without the signal transmitted during the call being recorded by the recording system 16. 506) "1 " means that a given tone frequency signal, e.g., "1", is received from the calling subscriber connection during the call, which signal is then routed to the SCP 15 controlling the recording system 16. 507) "Recording started" means that in response to a received tone frequency signal the recording system 16 is controlled to record the information transmitted between the calling subscriber connection 10 and the receiving subscriber connection 14 by means of the SCP 15. 508) "2" means that during a call, while the recording system 16 is recording information transmitted between the calling subscriber connection 10 and the receiving subscriber connection 14, a given or some other tone frequency signal, such as "2", is received from the calling subscriber connection and then routed to the SCP 15. 509) "Recording ended" means that in response to a tone frequency signal received from the calling subscriber connection 10 the recording system is by means of the SCP 15 controlled to stop recording the information transmitted between the calling subscriber connection 10 and the receiving subscriber connection 14. The telephone connection between three subscribers remains valid and the system is in a state corresponding to that of step 505. 510) "Call released" means that at a desired point in time during the telephone connection a signal of sufficient duration indicating desire to disconnect is received from the calling subscriber connection and or the receiving subscriber connection, and the telephone connection between three subscribers is discontinued. The obligation to receive an acceptable password may be restricted in a desired manner, e.g. it may be restricted to only cases where use of the recording system 16 is attempted from a subscriber connection other than one connected to a hotline service. The restriction may also be carried out on the basis of the identity of the calling subscriber such that certain calling subscriber identities do not presuppose the supplying of an acceptable password. It may be up to the client to decide which calling subscriber identities do not require the use of a password inquiry. The method according to the invention may also be applied as a dictaphone. Then the receiving subscriber connection 14 and connecting it are deleted from the arrangement. The method according to the invention may be used such that the recording system 16 is connected to an answering system, whereby the recording system serving as an answerer would also be utilized for recording calls. An element other than the SCP 15 can be used in the method according to the invention for controlling the recording system 16. Such an element may be e.g. an external server which receives control signals from a telephone exchange, an SCP 15 or some other element of the telephone network. The method according to the invention may be used via a telephone connection for recording optional information in digital form transmitted by means of e.g. a WAP phone. Hereby it is necessary to make sure that the signals controlling the recording system are filtered such that they do not get mixed up with the data to be recorded. Signals recorded by means of the recording system 16 under the control of the telephone subscriber may be recorded as a sound file which can be listened to e.g. via the WWW. The method according to the invention can be implemented such that speech transmitted over a telephone connection is recorded as a recording 24 and the recording 24 and/or some other recording is played back during the same telephone connection. This makes it possible to transmit the recording 24 to the receiving subscriber connection 14 in a case where the recording system 16 is controlled from the calling subscriber connection 10, or to the calling subscriber connection 10 when the recording system 16 is controlled from the receiving subscriber connection 14. Generally speaking the method according to the invention permits the utilization of all the facilities of the telephone network available when a group call between more than two subscriber connections is being carried out. In the present application, the term tone frequency signal is used to refer to Dual Tone Multiple Frequency (DTMF) signals controlling a telephone network. In the present application and in particular in the claims thereof the term calling subscriber connection refers to a subscriber cormection in a telephone or mobile network, which transmits a request to establish a connection, on the basis of which the telephone or mobile network seeks to establish a telephone or mobile connection to another telephone or mobile network subscriber connection/subscriber connection. In the present application and in particular in the claims thereof the term receiving subscriber connection refers to a subscriber connection in a telephone or mobile network which the telephone or mobile network seeks to establish a telephone or mobile connection with on the basis of a request to establish a connection received from the calling subscriber connection. In the present application and in particular in the claims thereof the term triggering action at the calling end refers to a rapid connection establishment to the target based on identifying the calling subscriber, this being linked to the identity of the calling subscriber connection in advance. Triggering action at the calling end is typically performed at the local exchange to which the calling subscriber connection is connected. In the present application and in particular in the claims thereof the term triggering action at the receiving end refers to a rapid cormection establishment to the target based on identifying the receiving subscriber, this being linked to the identity of the receiving subscriber cormection in advance. Triggering action at the receiving end is typically performed at the local exchange to which the receiving subscriber connection is connected. In the present application and in particular in the claims thereof the term call transfer refers to routing call requests to a given receiving network subscriber connection via a switched connection to some other network subscriber connection, the number of which is obtained from the information linked to the identity of the given receiving subscriber connection. This information is typically recorded at a local exchange close to the receiving subscriber connection. In the present application and in particular in the claims thereof the term group call refers to a telephone or mobile connection in which at least one telephone or mobile subscriber connection participates in addition to one calling and one receiving subscriber connection. In the present application and in particular in the claims thereof the term intelligent network exchange refers to a system connected to a telephone network which in a centralized manner takes measures presupposing more complicated or different data processing than those performed at telephone exchanges to control the telephone network.

Claims: Claims: 1. A method for recording calls under the control of a calling subscriber connection, comprising controlling a first recording system (16) in an operator's system which records information transmitted over a telephone connection on the basis of tone frequency signals received from the calling subscriber connection (10), characterized by receiving an off-hook signal of given length and a given number dialling from the calling subscriber connection (10) and in response to the off-hook signal of given length connecting the call to the first recording system (16) and in response to the given number dialling connecting the call to the receiving subscriber connection (14) or towards the receiving subscriber connection (14). 2. The method of claim 1, characterized by connecting the call to the first recording system (16) by means of a telephone exchange element permitting triggering action at the calling end. 3. The method of claims 1 to 2, characterized by in response to the given number dialling transmitting a signal to an intelligent network exchange by means of the telephone network element permitting triggering action at the calling end and connecting the call to the recording system (16) and to the receiving subscriber connection (14) or towards the receiving subscriber connection (14) under the control of the intelligent network exchange. 4. The method of claim 3, characterized in that the intelligent network exchange is an SSP (Service Switching Point) and/or an SCP (Service Control Point). 5. The method of any one of the claims 1 to 4, characterized by using a facility of the telephone network used for implementing group calls via the telephone network for connecting the first recording system (16) to the telephone connection between the calling subscriber connection (10) and the receiving subscriber connection (14). 6. The method of any one of the claims 1 to 5, characterized by controlling the first recording system (16) and/or a second recording system on the basis of tone frequency signals received from the receiving subscriber connection (14), and - in response to a given number dialling, transmitting a signal to the intelligent network exchange by means of the telephone exchange element permitting triggering action at the receiving end and connecting the call to the recording system ( 16) and to the receiving subscriber connection (14) or towards the receiving subscriber connection (14) under the control of the intelligent network exchange. 7. A method for recording calls under the control of a receiving subscriber connection, wherein the receiving subscriber connection (14) has a telephone number (28) and wherein a first recording system (16) or a second recording system in the operator's system recording information transmitted over a telephone connection is controlled on the basis of tone frequency signals received from the receiving subscriber connection (14), characterized by receiving a number dialling to the telephone number (28) from the direction of the calling subscriber connection (10), and in response to the number dialling to the telephone number (28) transmitting a signal to an intelligent network exchange by means of a telephone exchange element permitting triggering action at the receiving end, and connecting the call to the recording system (16) and to the receiving subscriber connection (14) or towards the receiving subscriber connection (14) under the control of the intelligent network exchange. 8. The method of claim 7, wherein the intelligent network exchange is an SSP (Service Switching Point) and/or an SCP (Service Control Point). 9. The method of any one of the claims 7 to 8, characterized by using a facility of the telephone network used for implementing group calls for connecting the first recording system (16) to the telephone connection between the calling subscriber connection (10) and the receiving subscriber connection (14). 10. The method of any one of the claims 7 to 9, characterized by receiving an off-hook signal of given length and a given number dialling from the calling subscriber connection (10) and in response to the off-hook signal of given length connecting the call to the first recording system (16) and in response to the given number dialling connecting the call to the receiving subscriber connection (14) or towards the receiving subscriber connection (14) and controlling the first recording system ( 16) in the operator ' s system, which transmits information transmitted over a telephone connection, on the basis of tone frequency signals received from the calling subscriber connection (10).

Inventors: JAUHIAINEN JUHA-PEKKA, JAUHIAINEN, JUHA-PEKKA
Applicants: ELISA COMM OYJ, JAUHIAINEN JUHA PEKKA, ELISA COMMUNICATIONS OYJ, JAUHIAINEN, JUHA-PEKKA
Application year: 2000
Main classification: H04M1
IPC codes: H04M3, H04Q1, H04Q3