Transformerless two-wire/four-wire hybrid with DC sourcing capability

摘要

An electronic hybrid circuit for coupling a two-wire communication path with a four-wire communication path is disclosed wherein the use of transformer coupling is eliminated. The hybrid features a novel arrangement whereby the unbalanced four-wire path incoming voice signal is amplified, then converted to a pair of balanced signal components by complementary signal injection devices coupled to opposite sides of the two-wire path. Each resultant balanced component is injected in series with a DC battery feed potential via current amplifiers in each signal injection means. Balanced two-wire path output signals are converted for transmission to the outgoing portion of the four-wire path by coupling the two-wire path to the series combination of a differential amplifier and an output buffer amplifier. A transhybrid balance network is connected between the output of one of the signal injection devices and the input of the buffer amplifier to prevent the coupling of signals from the incoming portion of the four-wire path from reaching the outgoing portion of four-wire path.