An experimental voice-frequency dialling system

An experimental voice-frequency dialling system is described for signalling between a telephone set with pushbutton caller and timedivision-multiplex switching system, in which the talking path and logical circuit are both time-shared. In order to get good matching between signal-receiving and time-shared logic, single voice-frequency signals sent from a station set are digitally recognized by a periodmeasuring counter in the register without demodulation. The paper discusses some signal-level and noise problems and gives some criteria for system design, together with experimental results. Further consideration is given to frequency allocation, number of cycles and recognition time, and a signal generator is also described.