Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Patent
1989-01-06
1991-01-29
Ng, Jin F.
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
379406, 379389, 370 32, H04L 514
Patent
active
049892363
ABSTRACT:
The invention concerns a transmission system for telephone communications comprising at least two telephone sets, each incorporating a microphone and a receiver and/or loudspeaker, and a telephone line connecting the telephone sets by at least two conductors in order to form a current loop. Connected to the current loop is an alternating-current generator and current-steering switch elements arranged to steer the current to be routed during the positive half-cycles generated by the generator via the microphone circuit of the first set and the receiver and/or loudspeaker circuit of the second set as well as to steer the current during the negative half-cycles via the receiver and/or loudspeaker circuit of the first set and the microphone circuit of the second set, whereby voice transmission takes place by sampling the microphone signals of the interconnected telephone sets and transmitting the alternate signal samples superimposed on the generator signal so that the microphone signal of the first set is superimposed on the positive half-cycles of the generator signal while the microphone signal of the second set is superimposed on the negative half-cycles of the generator signal. The invention is also applicable to data transmission, wherein the telephone sets are replaced by modems of a simple construction.
REFERENCES:
patent: 2980769 (1961-04-01), Lawsine et al.
patent: 4052562 (1977-10-01), Andersen
patent: 4326287 (1982-04-01), Abramson
patent: 4595803 (1986-06-01), Wright
patent: 4731798 (1988-03-01), Dirr
Ng Jin F.
Sostel Oy
Woo Stella L.
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