Mode switching and voltage regulator circuitry for a telephone a

Details Mode switching and voltage regulator circuitry for a telephone a Mode switching and voltage regulator circuitry for a telephone a

1975-12-17

1978-10-10

Cardillo, Jr., Raymond F.

Electricity: motive power systems

Motor-reversing

Armature or primary circuit control

318332, 330252, 330259, 330260, H04M 165

Patent

active

041198018

ABSTRACT:
In a telephone answering device, a bistable circuit employing a single operational amplifier is used for mode switching.
The bistable circuit uses feedback resistors from the operational amplifier output to respective inverting and non-inverting amplifier inputs. A capacitor is connected from a voltage terminal to one or the other input so as to force the amplifier output to an initial respectively high or low output state. If high, this state is maintained by selecting the feedback resistors to provide greater current into the non-inverting input. The low state is maintained by a voltage divider including the feedback resistor to the non-inverting input and another resistor to a voltage terminal that together keep the non-inverting input at below the threshold value. The circuit is switched by applying a triggering voltage to the appropriate input. In the answering device, the bistable circuit is used selectively to enable and disable the outgoing announcement and incoming message record amplifiers.

REFERENCES:
patent: 3430152 (1969-02-01), Walsh
patent: 3518519 (1970-06-01), Callan
patent: 3564444 (1971-02-01), Walsh
patent: 3586779 (1971-06-01), Chernack
patent: 3780226 (1973-12-01), Jacobson
patent: 3855511 (1974-12-01), Smith
patent: 3909537 (1975-09-01), Jacobson
patent: 3935390 (1976-01-01), Winterhulter
patent: 4044287 (1977-08-01), Ratzel

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