Signalling device for key telephone systems

Details Signalling device for key telephone systems Signalling device for key telephone systems

1975-09-05

1977-02-22

Cooper, William C.

179 18AD, H04M 172

Patent

active

040093549

ABSTRACT:
The present invention relates to a device which is to be used in conjunction with key telephone systems, as for example, intercom systems. More particularly, the invention consists of a device for decoding the pulse output from rotary dial telephones, indicating which digit has been dialed and selectively signalling the called party. Special features include acceptance of a wide range of pulse speeds and ratios with decoding immunity to the initial hookswitch closure and the last opening. The latter permits the digit "1" to be used, providing for an additional signal function. A decoding matrix operates a relay tree with provisions for either single or two-digit codes. The device is intended for use in key telephone systems which include rotary dial telephones.

REFERENCES:
patent: 3014097 (1961-12-01), Apt
patent: 3089000 (1963-05-01), Burgener
patent: 3668331 (1972-06-01), Warner
patent: 3670110 (1972-06-01), Warner
patent: 3725594 (1973-04-01), Cartwright
patent: 3739100 (1973-06-01), Cartwright
patent: 3941944 (1976-03-01), McIntosh

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