A robust approach to tele-control using DTMF signaling (telephone call transferring equipment)

A novel method is proposed which is effective in preventing malfunction in the DTMF (dual-tone multifrequency) signal decoder caused by the holding melody. When the monitoring time is one second, the probability of a malfunction is at most 0.01. The proposed approach is a double DTMF signal monitoring method using the statistical characteristics of a DTMF signal decoder for a holding melody. >