Browse Prior Art Database

Detection of Telephone Line Control Signals

IP.com Disclosure Number: IPCOM000052668D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Campbell, TM: AUTHOR

Abstract

A method of detecting equipment busy, extension busy and ring back telephone control signals is described. A speech processing system, as an example, detects and reacts to five call progress signals. A method for handling three of these signals is described here. The frequency and input occurrence characteristics of these three signals are as follows: Equipment Busy - 480 + 620 Hertz with 120 Interruptions per min. Extension Busy _ 620 + 620 Hertz with 60 Interruptions per min. Ring Back - 480 + 440 Hertz on 2 seconds and off 4 seconds The signals are illustrated in Fig. 1.

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Detection of Telephone Line Control Signals

A method of detecting equipment busy, extension busy and ring back telephone control signals is described. A speech processing system, as an example, detects and reacts to five call progress signals. A method for handling three of these signals is described here. The frequency and input occurrence characteristics of these three signals are as follows: Equipment Busy - 480 + 620 Hertz with 120 Interruptions per min. Extension Busy _ 620 + 620 Hertz with 60 Interruptions per min. Ring Back - 480 + 440 Hertz on 2 seconds and off 4 seconds The signals are illustrated in Fig. 1.

The circuits are shown in Fig. 2. The use of 480 Hertz tone detector 1 produces a square-wave signal from the input signal at 2. This signal is used to gate a chain of counters 3-5 driven by a 1 kilohertz oscillator 6. When the input signal is interrupted or the count reaches its maximum, the oscillator is degated under control of gate 7. At the same time, one of the line control status signals is gated out through circuit 8. Counter 3 performs a divide by ten function on a 1 kilohertz signal to produce a square-wave signal of a .01 second period. Counter 4 also performs a divide by ten function to output a signal of a .1 second period. The last counter 5 produces three outputs. One is a .2 second gate for equipment busy. The second output is a .4 second gate for extension busy. For the ring back signal a divide by ten function on the output of count...