Start circuit for telephone answering device

Details Start circuit for telephone answering device Start circuit for telephone answering device

1977-04-29

1978-09-26

Claffy, Kathleen H.

179 6E, H04M 164

Patent

active

041172728

ABSTRACT:
A start circuit for a telephone answering device for distinguishing between a standard 16 Hz bell signal with a repeating one second on -- two second off pattern, and extraneous dial signals having ten pulses or less. The number of sequential input pulses are accumulated in a first binary counter BC.sub.1 whose "4" and "8" stages are coupled to a NAND gate G.sub.4, and the number of successive input bursts each containing at least 12 pulses are accumulated in a second binary counter BC.sub.2 in response to the NAND gate output. A final, bell signal recognition output is produced when the second counter registers a predetermined count. The first counter is reset approximately 0.3 second after the termination of a first input burst in preparation for a possible second burst, while the second counter holds its count for approximately 5 seconds. The NAND gate output also disables the first counter after a count of 12 is reached.

REFERENCES:
patent: 3702904 (1972-11-01), Bard
patent: 3783193 (1974-01-01), Lee
patent: 3876836 (1975-04-01), Langan
patent: 4049916 (1977-09-01), Danner

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