Telephone line interface circuit

Details Telephone line interface circuit Telephone line interface circuit

1982-06-21

1984-02-21

Pellinen, A. D.

179 2DP, H04M 1100

Patent

active

044332122

ABSTRACT:
A circuit for coupling digital or analog data signals to a telephone line. A direct coupled transistorized circuit is disclosed having three different impedance conditions: on-hook, off-hook, and loop-test. Consequently, data can be transmitted regardless of the on-hook or off-hook status of the associated telephone sets and regardless of whether or not the telephone sets are in use. In addition, data transmission can range over a frequency spectrum of approximately d-c to frequencies in the data-over-voice range. Because of the variable bridging impedance, the drive impedance is not too low during on-hook ringing and the circuit need not be disconnected during ringing or testing.

REFERENCES:
patent: 4203006 (1980-05-01), Mascia
patent: 4224478 (1980-09-01), Fahey et al.
patent: 4321429 (1982-03-01), Takatsuki et al.
patent: 4378470 (1983-03-01), Murto et al.

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