Patent Publication Number: US-6909894-B1

Title: Echo plug for a wireless telephone

Description:
BACKGROUND OF THE INVENTION 
   FIELD OF THE INVENTION 
   The invention is related to the field of wireless communications, and in particular, to an echo plug that plugs into the hands-free jack of a wireless telephone to facilitate testing. 
   BACKGROUND OF THE INVENTION 
   The demand for wireless communication services is growing dramatically, and there is corresponding growth in the need to test wireless telephones and communication systems. A common testing technique uses a test system that is equipped with a transmit telephone circuit and a receive telephone circuit. The transmit telephone circuit places a test call to the receive telephone circuit over a wireless telephone. The transmit telephone circuit then transmits test signals over the call connection to the receive telephone circuitry. The test system compares the received test signals to the transmitted test signals to generate statistics regarding voice quality and round-trip delay. One example of a test system is the Voice Quality Tester supplied by Agilent Technologies. Two common voice quality measurements are Perceptual Speech Quality Measure (PSQM) and Perceptual Analysis Measurement System (PAMS). 
   The above-described test call is placed as follows. The transmit telephone circuit is connected to a wireless telephone using a special connector that is customized for the wireless telephone. The receive telephone circuit is connected to a telephone jack that is coupled to the communication network. The wireless telephone places a test call using a test telephone number. A wireless transceiver in the communication system handles the test call from the wireless telephone, and the communication system routes the call to the telephone jack. The receive telephone circuit that is connected to the telephone jack answers the call. The test system is now connected to a communications loop through the communication network and is ready to conduct voice quality and delay tests. 
   Wireless telephone suppliers and service providers need to test their equipment under various conditions to ensure quality. Unfortunately, the above-described testing technique inhibits robust testing under dynamic test conditions. For example, the test system is coupled to the wireless telephone with a special connector that is not compatible with other types of wireless telephones. Many wireless telephones do not have their own special connectors, and even if they did, the use of many different special connectors is cumbersome. As a result, the test system cannot effectively test many different types of wireless telephones. In addition to this restriction, mobility testing is cumbersome because the test system must be moved along with the wireless telephone. 
   The public telephone network internally performs similar tests. On a percentage of calls, the originating telephone switch requests a continuity test in the call set-up signaling message. In response to the request, the terminating telephone switch cross-connects the connections for the call. The originating telephone switch then transmits a tone to the terminating telephone switch where the tone is looped back to the originating telephone switch. The continuity test is successful if the originating telephone switch receives the tone. Continuity testing is inadequate to test wireless telephones and communication systems. 
   SUMMARY OF THE INVENTION 
   The invention solves the above problems with an echo plug that facilitates robust testing under dynamic test conditions by looping test signals through a wireless telephone back to a test system. The echo plug fits into the hands-free jack of a wireless telephone and is easily moved from one wireless telephone to another. The wireless telephones retain their mobility with the echo plug attached. The echo plug facilitates the testing of different wireless telephones at various locations over different communication systems. 
   One echo plug has a pin and a circuit. The pin is physically compatible with the hands-free jack of a wireless telephone. The pin has a speaker connection and a microphone connection. The circuit couples the speaker connection to the microphone connection. In operation, this echo plug receives a signal from the speaker connection of the hands-free jack and transfers the signal to the microphone connection of the hands-free jack. 
   Another echo plug has two pins and a circuit. The pins are physically compatible with the hands-free jack of a wireless telephone. The first pin has a speaker connection, and the second pin has a microphone connection. The circuit couples the speaker connection of the first pin to the microphone connection of the second pin. In operation, this echo plug receives a signal from the speaker connection of a hands-free jack in a first wireless telephone and transfers the signal to the microphone connection of a hands-free jack in a second wireless telephone. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram that illustrates system configuration in an example of the invention. 
       FIG. 2  is a schematic diagram that illustrates an echo plug in an example of the invention. 
       FIG. 3  is a schematic diagram that illustrates an echo plug with signal processing in an example of the invention. 
       FIG. 4  is a schematic diagram that illustrates signal processing components in an example of the invention. 
       FIG. 5  is a block diagram that illustrates system operation in an example of the invention. 
       FIG. 6  is a block diagram that illustrates system configuration in an example of the invention. 
       FIG. 7  is a schematic diagram that illustrates an echo plug in an example of the invention. 
       FIG. 8  is a schematic diagram that illustrates an echo plug with attenuation in an example of the invention. 
       FIG. 9  is a block diagram that illustrates system operation in an example of the invention. 
       FIG. 10  is a flow diagram that illustrates a testing method in an example of the invention. 
       FIG. 11  is a flow diagram that illustrates a testing method in an example of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   System Configuration— FIG. 1   
     FIG. 1  is a block diagram that illustrates system configuration in an example of the invention. The system includes communication system  100 , wireless telephone  110 , and test system  120 . Communication system  100  comprises jack  101  coupled to wireless transceiver  102  by communications path  103 . Communications path  103  could include multiple communication devices that are omitted for clarity. Wireless telephone  110  comprises hands-free jack  111  and communicates with wireless transceiver  102  over wireless link  112 . Hands-free jack  111  is configured with speaker and microphone connections that allow the connection of headsets and other audio devices to wireless telephone  110 . The speaker connection is sometimes referred to as “audio out”, and the microphone connection is sometimes referred to as “audio in”. Test system  120  is connected to jack  101  by telephone cable  121 . The above components could be conventional. 
   The system also includes echo plug  130  that is plugged into hands-free jack  111 . Echo plug  130  has a pin and pin handle that can be the similar to those of conventional hands-free plugs. Echo plug  130  is physically compatible with hands-free jack  111  of wireless telephone  110 . Echo plug  130  is configured with a speaker connection and a microphone connection that couple to their respective connections of hands-free jack  111 . Echo plug  130  also has a circuit that is configured to couple the speaker connection to the microphone connection. Thus, echo plug  130  loops the “audio out” of wireless telephone  110  back to the “audio in”. Advantageously, echo plug  130  facilitates testing by looping test signals back to test system  120 . 
   Echo Plug Configurations  FIGS. 2-4   
     FIGS. 2-4  depict specific examples of echo plugs in accord with the present invention. Those skilled in the art will appreciate variations from these example that do not depart from the scope of the invention. Those skilled in the art will also appreciate that various features described below could be combined to form multiple variations of the invention. 
     FIG. 2  is a schematic diagram that illustrates an echo plug in an example of the invention. Echo plug  230  comprises pin  231  and circuit  232 . Pin  231  is physically compatible with a 2.5 mm hands-free jack of a wireless telephone, although other sizes are used in other examples of the invention. Pin  231  has speaker connection  233 , microphone connection  234 , and ground connection  235 . Circuit  232  couples speaker connection  233  to microphone connection  234 . When echo plug  230  is plugged into the hands-free jack of a wireless telephone, signals that are sent to speaker connection  233  are looped back to microphone connection  234 . 
     FIG. 3  is a schematic diagram that illustrates an echo plug with signal processing components in an example of the invention. Echo plug  330  comprises pin  331  and circuit  332 . Pin  331  is physically compatible with a 2.5 mm hands-free jack of a wireless telephone, although other sizes are used in other examples of the invention. Pin  331  has speaker connection  333 , microphone connection  334 , and ground connection  335 . Circuit  332  couples speaker connection  333  to microphone connection  334  and includes signal processing components  336 . When echo plug  330  is plugged into the hands-free jack of a wireless telephone, signals that are sent to speaker connection  333  are transferred through signal processing components  336  and looped back to microphone connection  334 . 
     FIG. 4  is a schematic diagram that illustrates signal processing components  336  in an example of the invention. Signal processing components  336  comprise side-tone cancellation circuit  441 , delay circuit  442 , and attenuation circuit  443  coupled in series within circuit  332 . The order of circuits  441 - 443  within circuit  332  can vary. 
   In the typical telephone, side-tones are voice signals from the microphone that are fed back to the speaker so the caller can hear what they are saying. Side-tone cancellation circuitry is commonly employed in speaker phones to eliminate side tones. Side-tone cancellation circuit  441  cancels side-tones in a similar fashion to avoid a potential feedback loop created by circuit  332  and side-tone connections in the wireless telephone. 
   In telephone networks, the voice signal echoes off of wiring equipment at the listener&#39;s site back to the speaker&#39;s site. The speaker hears this echo of their own voice if the distances between the callers is great enough. To remove the annoying echo, echo cancellers in the communication system subtract a copy of the signal that is transmitted in one direction from the signal that is transmitted in the other direction. The subtraction is timed to coincide with the time the annoying echo reaches the echo canceller. Echo cancellers adversely impact testing using echo plug  330  because they attempt to cancel the test signal intentionally looped back by circuit  332 . Delay circuit  442  delays the test signal on circuit  332  past the time when echo cancellers remove echo. Thus, the echo cancellers remove ambient echo before the test signal from echo plug  330  reaches the echo canceller. 
   Some wireless telephones amplify the signals that are transferred to the speaker and that are received from the microphone. A test signal passing through echo plug  330  may be too powerful a signal for the microphone input. Attenuation circuit  443  reduces the strength of signals passing through echo plug  330  to offset any input level mismatch. One example of attenuation circuit  443  is a resister coupled between speaker connection  333  and microphone connection  334 , and a capacitor coupled between microphone connection  334  and ground connection  335 . 
   System Operation— FIG. 5   
     FIG. 5  is a block diagram that illustrates system operation in an example of the invention. The system is the same as depicted on FIG.  1  and includes communication system  100 , wireless telephone  110 , test system  120 , and echo plug  130 . Echo plug  130  is plugged into hands-free jack  111  of wireless telephone  110 . A test call is generated between test system  120  and wireless telephone  110  through communication system  100 . After the test call is answered, test system  120  transfers a test signal to the wireless telephone  110  over call paths  541 ,  542 , and  543 . Wireless telephone  110  transfers the test signal to the speaker connection of its hands-free jack  111 . Echo plug  130  provides call path  544  to return the test signal to the microphone connection of hands-free jack  111 . Echo plug  130  may apply side-tone cancellation, delay, and attenuation to the test signal on call path  544 . The microphone connection of hands-free jack  111  transfers the test signal to the transmit circuitry of wireless telephone  110 . Wireless telephone  110  transfers the test signal to test system  120  over call paths  545 ,  546 , and  547 . Test system  120  compares the received test signal to the transmitted test signal to generate statistics regarding voice quality and round-trip delay. 
   Alternate System Configuration— FIG. 6   
     FIG. 6  is a block diagram that illustrates an alternate system configuration in an example of the invention. The system includes communication system  600 , wireless telephone  610 , wireless telephone  615 , and test system  620 . Communication system  600  comprises jacks  601  and  604  respectively coupled to wireless transceiver  602  by communications path  603  and  605 . Communications paths  603  and  605  could include multiple communication devices that are omitted for clarity. Wireless telephones  610  and  615  respectively comprise hands-free jacks  611  and  616 . Wireless telephones  610  and  615  respectively communicate with wireless transceiver  602  over wireless links  612  and  617 , although they could communicate with separate transceivers in other examples of the invention. Hands-free jacks  611  and  616  are each configured with speaker and microphone connections. Test system  620  is respectively connected to jacks  601  and  604  by telephone cables  621  and  622 . The above components could be conventional. 
   The system also includes echo plug  630  that comprises plugs  630 A and  630 B that are connected by cable  630 C. Plug  630 A is plugged into hands-free jack  611 , and plug  630 B is plugged into hands-free jack  616 . Plugs  630 A and  630 B each have a pin and pin handle that can be the similar to those of conventional hands-free plugs. Plugs  630 A and  630 B are physically compatible with hands-free jacks  611  and  616 . Plugs  630 A and  630 B are each configured with a speaker connection and a microphone connection that couple to their respective connections of hands-free jacks  611  and  616 . Echo plug  630  has a circuit passing through cable  630 C that is configured to couple the speaker connection of plug  630 A to the microphone connection of plug  630 B. Thus, echo plug  630  loops the “audio out” of wireless telephone  610  to the “audio in” of wireless telephone  615 . Advantageously, echo plug  630  facilitates testing by looping test signals back to test system  620 . 
   The use of separate wireless telephones  610  and  615  effectively eliminates the side-tone and echo cancellation problems described with respect to FIG.  4 . There is no potential for an undesirable feedback loop between the echo plug  630  and side-tone circuitry in wireless telephones  610  or  615 . There is no echo cancellation between the separate connections from test system  620  to wireless telephones  610  and  615 . 
   Alternate Echo Plug Configurations  FIGS. 7-8   
     FIGS. 7-8  depict specific examples of echo plugs in accord with the present invention. Those skilled in the art will appreciate variations from these example that do not depart from the scope of the invention. Those skilled in the art will also appreciate that various features described below could be combined to form multiple variations of the invention. 
     FIG. 7  is a schematic diagram that illustrates an echo plug in an example of the invention. Echo plug  730  comprises plug  730 A coupled to plug  730 B by cable  730 C. Plugs  730 A and  730 B have respective pins  731 A and  731 B that are physically compatible with a 2.5 mm hands-free jack of a wireless telephone, although other sizes are used in other examples of the invention. Pin  731 A has a speaker connection  733 A, microphone connection  734 A, and ground connection  735 A. Pin  731 B has a speaker connection  733 B, microphone connection  734 B, and ground connection  735 B. Circuit  732  passes through cable  730 C to couple speaker connection  733 A to microphone connection  734 B. When echo plug  730  is plugged into the hands-free jacks of two wireless telephones, signals that are sent to speaker connection  733 A are looped back to microphone connection  734 B. 
     FIG. 8  is a schematic diagram that illustrates an echo plug with attenuation in an example of the invention. Echo plug  830  comprises plug  830 A coupled to plug  830 B by cable  830 C. Plugs  830 A and  830 B have respective pins  831 A and  831 B that are physically compatible with a 2.5 mm hands-free jack of a wireless telephone, although other sizes are used in other examples of the invention. Pin  831 A has a speaker connection  833 A, microphone connection  834 A, and ground connection  835 A. Pin  831 B has a speaker connection  833 B, microphone connection  834 B, and ground connection  835 B. Circuit  832  passes through cable  830 C to couple speaker connection  833 A to microphone connection  834 B through attenuation circuit  843 . When echo plug  830  is plugged into the hands-free jacks of two wireless telephones, signals that are sent to speaker connection  833 A are passed through attenuation circuit  843  and looped back to microphone connection  834 B. 
   Some wireless telephones amplify the signals that are transferred to the speaker and that are received from the microphone. A test signal passing through echo plug  830  may be too powerful a signal for the microphone input. Attenuation circuit  843  reduces the strength of signals passing through echo plug  830  to offset any input level mismatch. One example of attenuation circuit  843  is a resister coupled between circuit  832  from speaker connection  833 A and microphone connection  834 B, and a capacitor coupled between microphone connection  834 B and ground connection  835 B. 
   Alternate System Operation— FIG. 9   
     FIG. 9  is a block diagram that illustrates system operation in an example of the invention. The system is the same as depicted on FIG.  6  and includes communication system  600 , wireless telephones  610  and  615 , test system  620 , and echo plug  630 . Echo plug  630  is plugged into hands-free jacks  611  and  616  of respective wireless telephones  610  and  615 . A first test call is generated through communication system  600  between test system  620  and wireless telephone  610 . A second test call is generated through communication system  600  between test system  620  and wireless telephone  615 . After the test calls are answered, test system  620  transfers a test signal to the wireless telephone  610  over call paths  941 ,  942 , and  943 . Wireless telephone  610  transfers the test signal to the speaker connection of hands-free jack  611 . Echo plug  630  provides call path  944  to return the test signal to the microphone connection of hands-free jack  616 . Echo plug  630  may apply attenuation to the test signal on call path  944 . The microphone connection of hands-free jack  616  transfers the test signal to the transmit circuitry of wireless telephone  615 . Wireless telephone  615  transfers the test signal to test system  620  over call paths  945 ,  946 , and  947 . Test system  620  compares the received test signal to the transmitted test signal to generate statistics regarding voice quality and round-trip delay. 
   Testing Methods— FIGS. 10-11   
     FIG. 10  is a flow diagram that illustrates a testing method in an example of the invention for systems like that of FIG.  1 . The method starts by plugging the echo plug into the hands-free jack of a wireless telephone. A test call is then generated between the test system and the wireless telephone. The test system transmits a test signal to the wireless telephone over the test call. The echo plug loops the test signal from the speaker connection of the hands-free jack to the microphone connection of the hands-free jack. The wireless telephone transmits the test signal from the microphone connection of the hands-free jack to the test system over the test call. If mobility testing is desired at this time, then the wireless telephone is moved during test signal transmission. The test system generates test results in response to the first test signal. If there is another wireless telephone to test, then the echo plug is unplugged and plugged into the hands-free jack of the other wireless telephone. The above test sequence is repeated for the other wireless telephone. If mobility testing is desired at this time, then the wireless telephones are moved to a new test location, and the test sequence is repeated. 
     FIG. 11  is a flow diagram that illustrates an alternative testing method in an example of the invention for systems like that of FIG.  6 . The method starts by plugging the echo plug into the hands-free jacks of two wireless telephones. Two test calls are then generated between the test system and the two wireless telephones. The test system transmits a test signal to the first wireless telephone over the first test call. The echo plug loops the test signal from the speaker connection of the hands-free jack in the first wireless telephone to the microphone connection of the hands-free jack in the second wireless telephone. The second wireless telephone transmits the test signal from the microphone connection of the hands-free jack to the test system over the second test call. If mobility testing is desired at this time, then the wireless telephones are moved during test signal transmission. The test system generates test results in response to the first test signal. If there are other wireless telephones to test, then the echo plug is unplugged and plugged into the hands-free jacks of the two other wireless telephones. The above test sequence is repeated for the two other wireless telephones. If mobility testing is desired at this time, then the wireless telephones are moved to a new test location, and the test sequence is repeated. 
   The modularity of the echo plug provides for convenient testing of many different wireless telephones. After a wireless telephone is tested, the echo plug is easily moved to another wireless telephone for another test. This procedure can be repeated for many different wireless telephones because many wireless telephones have hands-free jacks. 
   Different communication systems can be tested by using two wireless telephones that are subscribed to the different communication systems. The test system places a first test call to the first wireless telephone over the first communication system and generates test results. The echo plug is then moved from the first wireless telephone to the second wireless telephone. The test system then places a second test call to the second wireless telephone over the second communication system and generates test results. 
   The mobility of the wireless telephone and echo plug provides convenient mobility testing. The wireless telephone and echo plug can be easily moved during or after the test. Mobility testing can be combined with the above testing techniques to test many different wireless telephones at many different locations over various communication systems. 
   Those skilled in the art will appreciate variations of the above-described embodiments that fall within the scope of the invention. As a result, the invention is not limited to the specific examples and illustrations discussed above, but only by the following claims and their equivalents.