Communication apparatus for generating a call signal from a tele

Details Communication apparatus for generating a call signal from a tele Communication apparatus for generating a call signal from a tele

1989-03-06

1990-07-17

Schreyer, Stafford D.

Telephonic communications

Telephone line or system combined with diverse electrical...

To produce visual-graphic copy

379350, 379418, H04M 1108

Patent

active

049426001

ABSTRACT:
A call signal generating circuit includes a DC/DC converter, an ON/OFF control unit, including a control circuit and a phototransistor, for ON/OFF-controlling an output voltage from the DC/DC converter, and a polarity inverter cooperating with the control circuit, for switching polarities of an ON/OFF-controlled voltage. The ON/OFF timings of the ON/OFF control unit and a polarity switching timing of the polarity inverter are adjusted to generate a call signal having an arbitrary frequency.

REFERENCES:
patent: 4660218 (1987-04-01), Hashimoto

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