Pulse or digital communications – Transceivers – Modems
Patent
1994-08-25
1996-04-09
Chin, Stephen
Pulse or digital communications
Transceivers
Modems
375377, 379 97, 379398, H04B 138, H04L 516
Patent
active
055068685
ABSTRACT:
Circuitry is described for providing a telephone line interface circuit of a MODEM for a computer with an AC impedance and DC voltage/current characteristics required by a given type telephone network such that the telephone line interface circuit can be matchingly connected with the given type telephone network. The given type telephone network provides an identification code representative of the required AC impedance and DC voltage/current characteristics. The circuitry comprises a plurality of impedance components that, when connected to the telephone line interface circuit, determine the AC impedance and DC voltage/current characteristics of the telephone line interface circuit. A plurality of terminals are coupled to receive a plurality of control signals associated with the identification code. A switching logic is coupled (1) between the plurality of impedance components and the telephone line interfacing circuit and (2) to the plurality of terminals for selectively connecting the plurality of impedance components to the telephone line interface circuit under the control of the plurality of control signals so as to cause the telephone line interface circuit to have the required AC impedance and DC voltage/current characteristics. An identifying circuit is coupled to the given type telephone network for identifying the required AC impedance and DC voltage/current characteristics by receiving the identification code and converting the identification code into the plurality of control signals.
REFERENCES:
patent: 4841561 (1989-06-01), Hill
patent: 4868863 (1989-09-01), Hartley et al.
"Incorporated Protection Circuit with Microcoded Switch Hook and Level Adjustment Functions," IBM Technical Disclosure Bulletin, vol 27, No. 28, pp. 4825-4826 (Jan. 1985).
"Une Interface Ligne Telephonique/Modem," Toute L'Electronique, No. 522, pp. 83-86 (Mar. 1987).
Cox Robert
Gradeler Eric
Hochfield Barry
Le Bars Philippe
Mohme Rodger J.
Apple Computer Inc.
Chin Stephen
Phan Hai H.
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