Telephonsystem, das einen Nachrichten-Wartezustand anzeigt

摘要

A telephone exchange system is described in which a ring drive signal is generated to a given called party in response to an incoming call or a voice message from a calling party, the ring drive signal having a different cadence if generated in response to a voice message than if generated in response to an incoming call. The ring drive signals are of the same voltage level. The ring drive signal is received in a telephone apparatus and an indicator is activated to indicate a message waiting. The different cadences result from signals having different duty cycles (fig.2). A third signal again having a different cadence is used to indicate that a call has originated from within the exchange. The indicator is either a neon lamp or an LED.