Digital calling signal tone generating circuitry

Details Digital calling signal tone generating circuitry Digital calling signal tone generating circuitry

1975-04-07

1976-05-25

Claffy, Kathleen H.

H04M 150

Patent

active

039596044

ABSTRACT:
Calling signals for tone-frequency telephone calling and like communications systems are generated in digital form. For the eight tone frequencies used in American telephone systems, a group of about 50 bits (average) for each tone is stored in an electronic store in delta modulation data form. Circuitry according to the invention is arranged for repetitively reproducing the contents of the store to produce a substantially continuous waveform. Bits for one high frequency band tone and one low frequency band tone are selectively reproduced and applied to a delta demodulation circuit for producing the desired tone-frequency analog signal. In a basic embodiment, start-stop operation is used for producing a calling signal for a single switching operation. A continuously operating tone frequency generating circuit embodiment is arranged for producing a multiple of continuously available tone signalling outputs. Both embodiments are readily constructed as Large Scale Integration (LSI) devices and readily arranged with the remainder of the communications lines switching circuit components in a central or branch exchange installation.

REFERENCES:
patent: 3128349 (1964-04-01), Boesch
patent: 3288940 (1966-11-01), Bennett
patent: 3381276 (1968-04-01), James
patent: 3456085 (1969-07-01), Huizinga
patent: 3515792 (1970-06-01), Deutsch
patent: 3772681 (1973-11-01), Skingle
patent: 3816635 (1974-06-01), Uetrecht
patent: 3826995 (1974-07-01), Miller
patent: 3882751 (1975-05-01), Tomisawa
patent: R25507 (1964-01-01), Meacham
R. L. Adams and F. A. Reiley, "Parallel Tone Generator Using Variable-Period Counters," IBM Tech. Disc. Vol. 15, No. 11, Apr. 1973, pp. 3457-3458.

Affiliated with

Also associated with

Rating

Digital calling signal tone generating circuitry does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Digital calling signal tone generating circuitry, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital calling signal tone generating circuitry will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-907504