| 摘要 |
<p>A precise tone injection circuit for injecting tone signals to a constant current junctor circuit in a two-wire balanced circuit. The tone injection circuit includes a pair of transistors operating as constant current sources feeding the respective ones of the two wires. A phase splitter amplifier couples a tone signal to the base electrodes of the transistors to change the current through their collector electrodes via the emitter circuits thereof at a rate and frequency of the tone signals at the base. Since a two-wire balanced circuit is used, and the injected signal currents to each wire are 180.degree. outof-phase, in-phase signals, that is, noise and voltage fluctuations, are reduced or rejected.</p> |
