1979-04-16
1981-11-17
Wolff, John H.
H04B 158
Patent
active
043013368
ABSTRACT:
Hybrid circuit for transition between two-wire and four-wire lines includes first and second operational amplifiers each having an inverted and non-inverted input and output, a voltage divider connected to each of the inverted inputs, a bidirectional terminal connecting the two-wire side to the non-inverted input of the first amplifier and a transmit terminal connecting the four-wire side to the non-inverted input of the second amplifier, to feed audio voltage to the non-inverted inputs, the voltage dividers having equal resistances, a receive terminal for connecting the four-wire side to the output of the first amplifier, matching impedances connected to the non-inverted input of the second amplifier and the output of the first amplifier, the matching impedances and an impedance balancing the impedance of the two-wire side compared to input impedances to the hybrid circuit being such that, for an incoming transmission, half of the output voltage of the second amplifier is at the non-inverted input of the first amplifier and, for an outgoing transmission, twice the input voltage to the first amplifier is at the output thereof, so that transmission loss in the hybrid circuit is zero in both directions, one of the amplifiers being operable for effecting phase reversal of an a-c voltage fed to the hybrid circuit from the four-wire side forming an asymmetric hybrid circuit; and a symmetric hybrid circuit including two of the asymmetric hybrid circuits.
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L. N. Jackson, "A Thick Film Electronic Hybrid Coil", Proceedings of I.R.E.E., Australia, vol. 36, No. 5, May 1975, pp. 117-118.
Deutsche Telephonwerke und Kabelindustrie Aktiengesellschaft
Lerner Herbert L.
Myers Randall P.
Wolff John H.
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