Telephonic communications – Centralized switching system – With generating of call associated substation signal
Patent
1985-11-14
1988-03-29
Dwyer, James L.
Telephonic communications
Centralized switching system
With generating of call associated substation signal
379418, H04M 302
Patent
active
047349360
ABSTRACT:
A circuit for sending out a ringing signal of a high voltage and a low frequency to a telephone set through a telephone line repeatedly with a predetermined time interval. In order to omit use of a high power oscillator and relays, a D.C. power supply of a high voltage is operatively connected to the telephone line through phototransistors of photocouplers being driven by a pulse signal having a low voltage and the low frequency under control of pulses occurring at the predetermined time intervals so that the ringing signal is sent out to the telephone set repeatedly with the predetermined time interval.
REFERENCES:
patent: 4220826 (1980-09-01), Kiss
Saito Masaaki
Tanaka Jouji
Tanimoto Yoshiji
Dwyer James L.
Nippon Telegraph and Telephone Corporation
Nitsuko Limited
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