Patent
1981-03-25
1983-03-29
Rubinson, G. Z.
179 2DP, H04M 1100
Patent
active
043784704
ABSTRACT:
Receive and transmit paths, for example for frequency shift keyed signals, are coupled to an interface circuit including a line transformer which is permanently connected to the telephone line via a high impedance. The effect of this high impedance on received signals is counteracted by an amplifier and/or a tuned circuit comprising a winding of the transformer. Switches in the interface circuit, responsive to received signals, serve to by-pass the high impedance, and reduce the gain of the amplifier and/or eliminate the effect of the tuned circuit, to permit normal coupling of signals between the telephone line and the receive and transmit paths.
REFERENCES:
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patent: 3842206 (1974-10-01), Barsellotti et al.
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IBM Technical Disclosure Bulletin, vol. 17, No. 2, Jul. 1974, pp. 477-478, Chrisfield, R. P., Wrage, R. H. "Time Sharing Circuit for Voice and FSK Data".
Alvey Stephen D.
Murto Tapio H.
Brady W. J.
Haley R. John
Northern Telecom Limited
Rubinson G. Z.
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