Telephone amplifier with switchable gain control

Details Telephone amplifier with switchable gain control Telephone amplifier with switchable gain control

1986-02-18

1988-09-20

Lev, Robert

Telephonic communications

Substation or terminal circuitry

Amplifying

379 52, H01M 160

Patent

active

047730889

ABSTRACT:
An amplifier for controlling the volume in a telephone instrument of the general type including coin-operated and pay type telephone instruments is enclosed in the telephone housing and provides a number of discrete, predetermined amplification levels selectable by operating a push-button switch also located in the housing so that its plunger extends through an opening in the telephone instrument face. The amplification level is automatically restored to a volume associated with a normal hearing sensitivity at the start of a new call and a dial shunt circuit suppresses the DTMF tones heard by a user when tone dialing is used.

REFERENCES:
patent: 2574887 (1951-11-01), Pye
patent: 2581251 (1952-01-01), Glazer et al.
patent: 3144513 (1964-08-01), Sherron
patent: 3254160 (1966-05-01), Day et al.
patent: 3902398 (1975-09-01), Nakada et al.
patent: 4151376 (1979-04-01), Walker, Jr.
patent: 4363934 (1982-12-01), Scholz
patent: 4385204 (1983-05-01), Wine
patent: 4466120 (1984-08-01), Walker, Jr. et al.
patent: 4568803 (1986-02-01), Frola
patent: 4608462 (1986-08-01), Blomley et al.
Mims, Forrest M., III, "Engineer's Notebook II", .COPYRGT.1982 by Radio Shack, p. 120.

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