Detection of Telephone Line Control Signals
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
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.