Transformerless trunk circuit

摘要

A transformerless two-way trunk circuit particularly useful for interconnecting a balanced lead pair and an unbalanced lead pair, with complete control over sidetone and signal level. The balanced lead pair is terminated with a first matching A.C. impedance and a second D.C. resistance means. A first transformerless circuit means applies an incoming signal from the unbalanced lead pair to the balanced lead pair, and a second transformerless circuit means applies an incoming signal from the balanced pair to the unbalanced lead pair. A third transformerless circuit means cancels signals from said first circuit means applied to the balanced lead pair to prevent them from being reapplied to the unbalanced lead pair, and a fourth transformerless circuit means cancels signals from said second circuit means applied to the unbalanced lead pair to prevent them from being reapplied to the balanced lead pair.