HV protection circuit for telephone subscriber's appts. - disconnects upon application of excess voltage and reconnects when voltage falls with potential tapping at indication circuit

摘要

The circuit connects a subscriber appts. (TE) to a remote exchange. A supply circuit provides electric power via the exchange line. An indication circuit (INW) enables certain conditions of the appts (TE) to be detected. The circuit is protected by interrupting the current flow through the along the line when an excess external voltage is applied and is immediately detected by the indication circuit which also detect when the voltage has fallen back below a given level. ADVANTAGE - Detects and indicates when the voltage falls again to safe working level.