Telephone line quality testing system
First Claim
1. A telephone line quality testing system for use in a message transmitting system having at least two subsystems which can be interconnected by a telephone connection, each subsystem having message storage means for storing messages, said telephone line quality testing system comprising:
- call initiating means in a first subsystem for establishing a telephone connection with a second subsystem;
communication protocol means in the first subsystem coupled to said telephone connection for transmitting packets of DTMF tones to the second subsystem via the telephone line connection, and for receiving DTMF tones transmitted by the second subsystem via the telephone connection;
response generating means in the second subsystem coupled to said telephone connection for receiving packets of DTMF tones transmitted by the first subsystem, and for responding to each said packet by transmitting a responsive packet of DTMF tones, said responsive packet including a marker comprising at least one DTMF tone selected from the set of DTMF tones not used in at least a predefined portion of the DTMF tones received from said first subsystem; and
echo detection means in the first subsystem coupled to said communication protocol means in the first subsystem for generating a comparand identical to the marker which the second subsystem would generate if the second system properly received the last packet sent to it, and for generating an error signal if said comparand does not match a predefined portion of the DTMF tones received from the telephone connection.
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Accused Products
Abstract
A telephone line quality testing system detects line echoes in the telephone connection between two subsystems in a message transmission system. The test for line echoes is performed while the two subsystems exchange identification data by transmitting DTMF signals in a predefined sequence. Each subsystem transmits a marker at the beginning of each DTMF transmission. This marker is constructed so that it can be distinguished, with absolute certainty, from any possible echo of the previous DTMF transmission by the other subsystem. In general, the marker includes at least one DTMF signal selected from the set of DTMF signals not included in the last X DTMF signals sent by the other subsystem. Each subsystem also generates an "Expected marker" that should precede the next DTMF transmission by the other subsystem. When receiving a DTMF transmission, each subsystem compares the initial DTMF signals received with the expected marker. If a match is found, the first DTMF signal which matches the expected marker is denoted as the beginning of the received packet and the DTMF signals preceding that signal, if any, are discarded as line echoes. If none of the initial (e.g., fourteen) signals received match the expected marker the call is terminated because a line quality problem has been detected.
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Citations
12 Claims
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1. A telephone line quality testing system for use in a message transmitting system having at least two subsystems which can be interconnected by a telephone connection, each subsystem having message storage means for storing messages, said telephone line quality testing system comprising:
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call initiating means in a first subsystem for establishing a telephone connection with a second subsystem; communication protocol means in the first subsystem coupled to said telephone connection for transmitting packets of DTMF tones to the second subsystem via the telephone line connection, and for receiving DTMF tones transmitted by the second subsystem via the telephone connection; response generating means in the second subsystem coupled to said telephone connection for receiving packets of DTMF tones transmitted by the first subsystem, and for responding to each said packet by transmitting a responsive packet of DTMF tones, said responsive packet including a marker comprising at least one DTMF tone selected from the set of DTMF tones not used in at least a predefined portion of the DTMF tones received from said first subsystem; and echo detection means in the first subsystem coupled to said communication protocol means in the first subsystem for generating a comparand identical to the marker which the second subsystem would generate if the second system properly received the last packet sent to it, and for generating an error signal if said comparand does not match a predefined portion of the DTMF tones received from the telephone connection. - View Dependent Claims (2, 3, 4)
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5. A telephone line quality testing system for use in a message transmitting system having at least two subsystems which can be interconnected by a telephone connection, each subsystem having message storage means for storing messages, said telephone line quality testing system comprising:
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call initiating means in a first subsystem for establishing a telephone connection with a second subsystem; first and second communication protocol means in the first and second subsystems, respectively, each said communication protocol means coupled to said telephone connection for transmitting packets of DTMF tones to the other subsystem via the telephone line connection, and for receiving DTMF tones transmitted by the other subsystem via the telephone connection; first and second marker generating means in the first and second subsystems, respectively, each said marker generating means coupled to said telephone connection for receiving packets of DTMF tones transmitted by the other subsystem, and for responding to at least one of said received packets by generating a marker to be transmitted to the other subsystem as part of the next packet to be sent to the other subsystem, said marker comprising at least one DTMF tone selected from the set of DTMF tones not used in at least a predefined portion of DTMF tones received from the other subsystem; and first and second echo detection means in the first and second subsystems, respectively, each said echo detection means coupled to said communication protocol means in the same subsystem for generating a comparand identical to the marker which the other subsystem would generate if the other system properly received the last packet sent to it, and coupled to said telephone connection for receiving DTMF tones transmitted by the other system and for generating an error signal if said comparand does not match a predefined portion of the DTMF tones received from the telephone connection. - View Dependent Claims (6, 7, 8)
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9. A method of testing telephone line quality for use by a message transmitting system having at least two subsystems which can be interconnected by a telephone connection, each subsystem having message storage means for storing messages, the steps of method comprising:
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establishing a telephone connection between a first subsystem and a second subsystem; transmitting at least one packet of DTMF tones from the first subsystem to the second subsystem via said telephone connection; responding to at least one of said packets transmitted by the first subsystem, when received by the second subsystem, by transmitting a responsive packet of DTMF tones from the second subsystem to the first subsystem via said telephone connection, said responsive packet including a marker comprising at least one DTMF tone selected from the set of DTMF tones not used in at least a predefined portion of the DTMF tones received from the first subsystem; generating a comparand identical to the marker which would be generated if the second subsystem properly received the last packet sent by the first subsystem to the second subsystem; and generating an error signal for use by the first subsystem if said comparand does not match a predefined portion of the DTMF tones received by the first subsystem from the telephone connection. - View Dependent Claims (10, 11, 12)
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Specification