Abstract:
An audio interface includes interface circuitry configured to translate audio signals received from a military handset to audio signals compatible with a plain old telephone system (POTS) network. The interface circuitry presents a 6-pin (or 5-pin) audio port configured to couple the military handset to the interface circuitry. The interface circuitry further features a 2-wire POTS connector configured to couple the interface circuitry to the POTS network.

Description:
BACKGROUND 
     This document relates to telecommunication audio interfacing. 
     Communication equipment configured to access the broadband global area network offers the user a range of secure and non-secure data and legacy voice services. The terminal  100  shown in  FIG. 1  provides a secure data connection over a commercial satellite communication system  140 . The terminal  100  also provides connectivity to a non-secure, plain old telephone system (POTS) network  150 , via the commercial satellite communication system  140 . In order to carry out a call over a secure military communication system (not pictured), the caller uses a military handset  115  plugged into a legacy audio module  110  via a 6/5-pin audio port. 
     Alternately, to make a call on the POTS network  150 , the caller uses a POTS telephone  125  plugged into a POTS interface module  120  via a connector, for example a 2-pin registered jack (RJ-11). The terminal  100  includes a POTS link I/O module  130  to provide connectivity to the POTS network  150 , via a POTS link over the commercial satellite system  140 . Typically, the POTS link I/O module  130  features a high speed modem. Using the terminal  100  configured as illustrated in  FIG. 1 , one caller uses a POTS telephone  125  to make or receive calls to or from a second caller  160  on the POTS network  150 . As shown in  FIG. 1 , the terminal  100  is ready for use under various conditions and from various locations. 
     SUMMARY 
     Systems and techniques for interfacing telecommunication audio are described. In one aspect, an audio interface includes interface circuitry configured to translate audio signals received from a military handset to audio signals compatible with a POTS network. The interface circuitry presents a 6-pin (or 5-pin) audio port configured to couple the military handset to the interface circuitry. The interface circuitry further has a 2-wire POTS connector configured to couple the interface circuitry to the POTS network. 
     This and other aspects can include one or more of the following features. In another aspect of the audio interface, the interface circuitry includes tone circuitry configured to add a POTS network dial tone to the audio signals. The interface circuitry features a first buffer configured to provide impedance matching between the military handset and the tone circuitry. The interface circuitry includes a phone line interface (PLI) circuitry configured to convert a format of the audio signals between a military handset format and a POTS network format. The converting step includes conditioning and isolating the audio signals. Furthermore, the interface circuitry includes volume circuitry configured to provide volume control for the audio signals. Also, the interface circuitry features a second buffer configured to provide impedance matching between the volume circuitry and the military handset. The audio port can be a 6-pin U-229 or a 5-pin U-183 connector. The 2-wire POTS connector can be a surface mount connector when the audio interface is coupled to the POTS network through a high speed modem. Also, the 2-wire POTS connector can be an RJ-11 connector when the audio interface is coupled to the POTS network through a landline. 
     In another implementation, a telecommunications system includes a telecommunications terminal having connectivity to both satellite and a POTS network. The telecommunications terminal contains an audio interface. The audio interface includes interface circuitry configured to translate audio signals received from a military handset to audio signals compatible with a POTS network. The interface circuitry presents a 6-pin (or 5-pin) audio port configured to couple the military handset to the interface circuitry. The interface circuitry further has a 2-wire POTS connector configured to couple the interface circuitry to the POTS network. 
     This and other aspects can include one or more of the following features. In another aspect of the telecommunications system, the interface circuitry includes tone circuitry configured to add a POTS network dial tone to the audio signals. The interface circuitry features a first buffer configured to provide impedance matching between the military handset and the tone circuitry. The interface circuitry includes a phone line interface (PLI) circuitry configured to convert a format of the audio signals between a military handset format and a POTS network format. The converting step includes conditioning and isolating the audio signals. Furthermore, the interface circuitry includes volume circuitry configured to provide volume control for the audio signals. Also, the interface circuitry features a second buffer configured to provide impedance matching between the volume circuitry and the military handset. The audio port can be a 6-pin U-229 or a 5-pin U-183 connector. The 2-wire POTS connector can be a surface mount connector when the audio interface is coupled to the POTS network through a high speed modem. Also, the 2-wire POTS connector can be an RJ-11 connector when the audio interface is coupled to the POTS network through a landline. 
     In another aspect, audio signals are received from a military handset at the audio interface. The received audio signals are further prepared for transmission through a POTS network. The prepared signals are output to the POTS network. 
     This and other aspects can include one or more of the following features. In another aspect, the audio signals are prepared by adding a POTS network dial tone, while providing impedance matching between the military handset and the tone circuitry. Furthermore, the format of the audio signals is converted between a military handset format and a POTS network format. During the converting step the audio signals are conditioned and isolated. Also, the audio signals are prepared by providing volume control, while providing impedance matching between the volume circuitry and the military handset. The audio signals can be received via a multi-pin audio port. The prepared audio signals can be output via a 2-wire POTS connector. 
     Certain implementations may provide various advantages. For example, the audio interface my enable callers to communicate directly between equipment connected to a radio transceiver 6-pin (or 5-pin) audio connector and 2-wire POTS equipment. Further aspects, features and advantages will become apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a communication terminal connected to a secure satellite communication system and separately to a POTS network via a non-secure satellite communication system. 
         FIG. 2  is a schematic representation of an audio interface. 
         FIG. 3  is a schematic representation of the functional blocks of an audio interface. 
         FIG. 4  is a schematic representation of an audio interface module. 
         FIG. 5  is a schematic representation of a terminal configured with an audio interface. 
         FIG. 6(   a ) is a schematic representation of an implementation of the audio interface. 
         FIG. 6(   b ) is a schematic representation of an implementation of the audio interface. 
         FIG. 7(   a ) is a schematic representation of an implementation of the audio interface. 
         FIG. 7(   b ) is a schematic representation of an implementation of the audio interface. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 2 , an audio interface  200  enables a first caller to use a rugged, typically military, 6-pin (or 5-pin) audio device  215  to directly make or receive calls to or from a second caller  260  on the POTS network  250 . 
     The audio device  215  is coupled to the input  210  of the audio interface  200 . The output  245  of the audio interface  200  is coupled to a POTS link I/O module  230 . In this example, the POTS link I/O module  230  is used to provide connectivity to the POTS network  250  via a satellite POTS link  240 . Typically, the POTS link I/O module  230  features a high speed modem. In another implementation, when the POTS link is a landline, the POTS link I/O module  230  may be omitted, and the landline plugs directly into the output  245  of the audio interface. 
     The external and internal functionality of the audio interface  200  is illustrated diagrammatically in  FIG. 3 . An audio device, such as an H-250 or H-350 6-pin (or 5-pin) military handset  215 , is coupled to an audio port  310  of the audio interface  200 . The voice signal from the microphone of the 6-pin (or 5-pin) military handset  215  is received into the 6-pin (or 5-pin) audio port  310  and processed by a first buffer circuitry  320 . The voice signal to the earphone of the 6-pin (or 5-pin) military handset  215  is sent from the 6-pin (or 5-pin) audio port  310  after it was processed by a second buffer circuitry  315 . The buffer circuitry  320  and  315  provides signal buffering and impedance matching between the audio port  310  and a tone/volume circuitry  325 / 330 . 
     The audio signals are processed by the tone/volume circuitry  325 / 330 . The dual-tone multi-frequency (DTMF) tone circuit  325  adds dial tone information required by POTS equipment to make a telephone call. The volume circuit  330  performs volume control for the earphone audio signal. 
     The phone line interface (PLI) module  340  is used to make telephony connections between terminal  100  and the POTS network  250 . The PLI module  340  processes the audio signals from/to tone/volume circuit  325  and  330 , including conditioning, isolating and converting the audio signals to a format that is compatible with telephony networks worldwide. 
     Finally, the POTS signals are exchanged between the audio interface  200  and POTS link I/O module  230  through a 2-wire POTS I/O connector  345 . In doing so, the audio interface  200  allows for a direct telephone connection between the 6-pin (5-pin) military handset  215  and a desk phone  260  residing on (or part of) the POTS network  250 . 
     The POTS “tip” signal and the “ring” signal typically provide DC current to power telephone electronics. The POTS “tip” signal and the “ring” signal also provide AC current to ring the telephone bell or electronic ringer. Furthermore, the POTS “tip” signal and the “ring” signal provide and a full duplex balanced voice path). The audio interface  200  translates the POTS “tip” and “ring” signals into the signals required by audio/data equipment  215  connected to, for example, the U-229 family (6-pin) military standard audio connector. The audio interface  200  also translates the signals from the audio/data equipment  215  connected to the U-229 family (6-pin) military standard audio connector into signals required by the audio/data equipment  260  connected to a 2-wire POTS connector (for example an RJ-11 connector). Therefore, the audio interface  200  allows telephone calls and/or data exchanges between POTS equipment such as a desk phone  260  and equipment such as an H-250 or H-350 military handset  215 . 
     Ultimately, the audio interface  200  provides an integrated device to enable a person using a 6-pin (or 5-pin) military handset  215  to make or receive full-duplex calls to or from a 2-wire POTS network  270 . 
     The audio interface  200  of  FIG. 3  may be implemented as an audio interface module  400  as exemplified in  FIG. 4 . An audio port  410  mounted on a face plate of the audio interface module  400  may be a connector from the U-229 (6-pin) or the U-183 (5-pin) families of military standard audio connectors. The audio port  410  corresponds to the audio interface input  210 . A POTS I/O connector  445  is mounted on the back face of the audio interface module. The POTS I/O connector  445  corresponds to the audio interface output  245 . In one implementation, the 2-wire POTS I/O connector  445  may be a MOLEX® 43045-1414 surface mount connector providing connectivity to a high speed modem included in a POTS link I/O module  230 . In another implementation, the POTS I/O connector  445  may be a 2-wire RJ-11 connector providing direct connectivity to the POTS network  250  via a landline. 
     The audio interface module  400  may include at least one printed circuit board (PCB) configured to mechanically support and electrically connect electronic components performing the functions of the audio interface  200 . In the example depicted in  FIG. 4 , the audio interface module  400  includes two PCBs, the first PCB  420  coupled to the 6-pin (or 5-pin) audio port  410 , and the second PCB  430  coupled to the POTS I/O connector  445 . The functionality of the circuitry corresponding to each PCB is described below. 
     The audio interface  200  implemented as the audio interface module  400  illustrated in  FIG. 4  may be integrated into rugged communication equipment (terminals) configured to use 6-pin (or 5-pin) military handsets. Examples of such terminals are Multi-band SATCOM, and LOS radios like the AN/PSC-5 or the PRC-117F. An example illustrating integration of the audio interface module  300  into an Inmarsat terminal, like the ViaSat PSC-14 is presented in  FIG. 5 . 
     Referring to  FIG. 5 , the terminal  100  may include a 6-pin (or 5-pin) audio interface module  110  to enable calls over a secure satellite communication system. The terminal  100  may also include a POTS interface module  120  to enable calls over a POTS network, if POTS compatible telephone equipment is available to the terminal operator. Communications using modules  110  and  120  were also illustrated in  FIG. 1 . Returning to  FIG. 5 , the terminal  100  may also include a 6-pin (or 5-pin) to 2-wire audio interface module  400 . By integrating the audio interface module  400 , the users of the terminal  100  are able to make or receive calls to or from the POTS network  150 , even when a standard POTS telephone is not available, by using a 6-pin (or 5-pin) military handset  115 . 
       FIG. 4  illustrates and exemplary implementation of the audio interface module  400 . The layout of the first PCB  420  connected to the 6-pin (or 5-pin) audio port  410  is drawn in  FIG. 6(   a ). In this exemplary implementation, the first PCB  420  is also referred to as the operator interface. The layout of the second PCB  430  connected to the 2-wire POTS I/O connector  445  is drawn in  FIG. 7(   a ). In this exemplary implementation, the second PCB  430  is also referred to as the terminal interface. 
     Referring to  FIG. 6(   a ), in an exemplary implementation the buffer circuitry  315 / 320  may be positioned on the first PCB  420 . The components and layout of the buffer circuitry are detailed in  FIG. 6(   b ). The first buffer circuitry  320  features an Analog Devices SSM2167 variable gain operational amplifier specifically designed for microphone applications. The first buffer circuitry  320  provides an output that meets the electrical requirements of the Tone/Volume circuit  325 / 330  to which it is connected. 
     Returning to the exemplary implementation of  FIG. 6(   a ), the second buffer circuitry  315  may also be positioned on the first PCB  420 . The components and layout of the second buffer circuitry  315  are detailed in  FIG. 6(   b ). The second buffer circuitry  315  features an Analog Devices OP177 fixed gain operational amplifier. The second buffer circuitry  315  provides an output that meets the electrical requirements of the military handset  115  to which it is connected. 
     Referring to  FIG. 7(   a ), in an exemplary implementation the tone/volume circuitry  325 / 330  may be positioned on the second PCB  430 . The components and layout of the tone/volume circuitry  325 / 330  are detailed in  FIG. 7(   b ). The tone generator circuit  325  generates standard dual-tone multi-frequency (DTMF) tones and features a Zarlink Semiconductor MT88L85 DTMF tone generator. The volume circuit  330  provides volume control for the military handset  115  and features an Analog Devices AD5247 digital potentiometer. The PLI module  340  converts both earphone and microphone signals into a format suitable for a 2-POTS network. The PLI module  340  features a Clare CPC5622 phone line interface. 
     The first PCB  420  and second PCB  430  are coupled together via a flexible circuit. The flexible circuit is connected to the first PCB  420  and to the second PCB  430  via surface-mounted connectors. The audio interface module  400  may be implemented on single PCB which integrates all functions provided by the buffer circuitry  315 / 320 , the tone/volume circuitry  325 / 330 , and the PLI circuitry  340 . 
     Furthermore, the audio interface  200  may be implemented as a removable audio interface module  400  which plugs in and out of a terminal  100 . The audio interface may be implemented as one or more PCBs permanently attached inside the terminal  100 . In another implementation, the audio interface  200  may be integrated onto the motherboard of a terminal  100 . Other implementations are within the scope of the following claims.