High voltage message waiting circuit

摘要

A message waiting circuit comprised of a pair of electrical leads which carry a message waiting signal, a capacitor for storing electrical energy extracted from the message waiting signal, a transistor for allowing the capacitor to charge when the message waiting signal is within a predetermined range; a Darlington transistor for causing the capacitor to discharge; and a light emitting diode (LED) which emits light when the capacitor discharges. The flashing LED indicates that a message is waiting for a user of the telephone set associated with the message waiting circuit. Approximately ten to twenty-five message waiting circuits and associated telephone sets can be connected to a single telephone line.