Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1986-09-02
1988-01-19
Schreyer, Stafford D.
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379347, 379420, H04M 102, H04M 910
Patent
active
047208562
ABSTRACT:
A DC control loop is disclosed which is used in conjunction with a control circuit to precisely set the maximum control voltage produced by the control circuit for maximizing the gain of an attenuator controlled thereby. The attenuator includes a current mirror having an output for sourcing a DC current the magnitude of which is proportional to the gain of the attenuator and the control circuit includes a capacitor that is charged or discharged accordingly to vary the magnitude of the control voltage. The DC control loop includes a circuit for sinking the current supplied from the current mirror and a current of a predetermined magnitude, the circuit being coupled to the output of the current mirror and a transistor which is turned on when the magnitude of the current from the current mirror equals the magnitude of the current sank by the circuit to inhibit further charge or discharge of the capacitor whereby the gain of the attenuator is held at a predetermined maximum value.
REFERENCES:
patent: 4608462 (1986-08-01), Blomky et al.
patent: 4648110 (1987-03-01), Elsasser
Pace W. David
Welty Dennis L.
Bingham Michael D.
Motorola Inc.
Schreyer Stafford D.
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