Control circuitry for a tape cassette telephone answering device

Claim 1

A control circuit for a telephone answering device of the type which is connectable to a telephone line and in which an outgoing announcement initially is transmitted to the telephone line after which messages incoming from the telephone line are recorded during an incoming message recording period, and having a mid-cycle mode transfer circuit to transfer operation of said device from the outgoing announcement transmission mode to the incoming message recording mode, and having a turn-off circuit to return said device to an off or standby condition after completion of operation in the incoming message recording mode, said device comprising: a tone burst oscillator actuated at the end of outgoing announcement transmission and at the end of an incoming message recording period, said oscillator when so actuated respectively producing first and second audio tone bursts each superimposed on a DC component, the output of said tone burst oscillator being connected to both the mid-cycle mode transfer circuit and to the turn-off circuit of said device via a steering circuit means operative to provide the DC component of the first audio tone burst to said transfer circuit to initiate said mid-cycle mode transfer, and operative to supply the DC component of the second audio tone burst to said turn-off circuit to cause the same to return said device to an off or standby condition, and wherein said steering circuit means comprises; a pair of resistors connected in series between the output of said tone burst oscillator and the input of said turn-off circuit, and a diode connected from the junction of said pair of resistors to a voltage source which is provided only when said device is conditioned to the incoming message record mode, the output of said tone burst oscillator also being directly connected to said mid-cycle mode transfer circuit, upon occurrence of said first audio tone burst the junction of said pair of resistors is effectively grounded via said diode so that said DC component is not supplied to said turn-off circuit but only to said mid-cycle mode transfer circuit, and where thereafter, as a result of the voltage source provided to said diode only when said device is in the incoming message record mode, the DC component of said second audio tone burst is supplied via said pair of resistors to said turn-off circuit to cause the same to return said device to an off or standby condition.