Touch-Tone Spurious Triggering Prevention
Original Publication Date: 1979-Nov-01
Included in the Prior Art Database: 2005-Feb-20
A variety of tone-coded telephone signalling systems exists. In a voice store and forward system, voice is stored on a disc or tape and is transmitted via telephone circuits to a listener or user under control of a host CPU. By using tone control keys on the telephone instrument, the user can signal the CPU to control start up, stop speed up, slow down, etc., of the voice signals stored on the medium employed. Tone signalling, as used in the telephone industry, consists of simultaneously transmitted dual tones chosen from an A tone set and a B tone set. There are 16 possible combinations of tones, although most telephones are provided with only 12 combinations. When these pairs of tones are received at a receiver decoder, a single output line (1 out of 12 or 1 out 16) is energized.