Telephone having separate voice and signaling pairs

摘要

A telephone station set (S1) is arranged to communicate voice signals over a voice communication pair (V1) and to communicate ringing, switchhook supervision and visual signaling over a separate signaling pair (C1). An amplitude and polarity modulated alternating voltage on the signaling pair (C1) provides current flow in one direction for visual signaling while distinguishable amounts of current flow in the opposite direction to provide switchhook and ringing supervision. The switchhook supervision current and the ringing signal current both flow through a series connection of a buzzer (B1) and a break switchhook contact (SH2) in the telephone station set. An off-hook condition at the telephone interrupts current flow on the signaling pair (C1) providing a switchhook supervision signal while simultaneously terminating the ringing signal.