In this telephone answering device, a new outgoing announcement can be recorded under remote control via the telephone line. To accomplish this, the user calls his own number. During the incoming message record portion of the resultant answering cycle, the user sends a coded signal over the telephone line. As a result, the message tape is stopped, and the announcement tape is driven. As the user then speaks the new announcement, it is amplified and recorded onto the announcement tape instead of onto the message tape. Switching circuitry is minimized since the amplifier already is conditioned for operation in the incoming message record mode. In addition, the prior announcement is erased, and generation of the audio tone which normally occurs at the end of the outgoing announcement is inhibited. When the new announcement has been recorded, the device automatically returns to the announcement transmit portion of the answering cycle. The new message is played out for verification. The device completes the answering cycle and shuts down in readiness for the next call. Another answering device is disclosed in which the outgoing announcement is contained in digital format in a read only memory. When a call is answered, the memory is read out and the contents are converted to audio by a speech synthesizer or a microprocessor that is programmed to decode speech compression encoded signals.

A pre-amplifier circuit comprises an operation amplifier having a noninverting input terminal connected to a voice input terminal, a negative feedback circuit having a first resistor which is connected between an output terminal of the operation amplifier and an inverting input terminal of the operation amplifier, and a second resistor and a switching element which are connected in series between the inverting input terminal of the operation amplifier and a ground, an operating switch for switching a small signal input mode and a large signal input mode, and an on-off control circuit for bringing the switching element into an off state to operate the operation amplifier as a buffer circuit when the operating switch is switched to the large signal input mode, while bringing the switching element into an on state to operate the operation amplifier as an amplifier circuit when the operating switch is switched to the small signal input mode.

In this telephone answering device, the outgoing and incoming audio amplifiers are interconnected to function as a mode switching flip-flop. Remote playout is enabled upon detection of the first beep tone. This sets a control flip-flop which consists of a single operational amplifier interconnected with a steering capacitor to function as a toggleable bistable circuit. A cylindrical cam mechanism and associated control circuit are actuated by setting of the remote playout control flip-flop. These cooperate with a reel drive motor first to rewind the message tape and then to drive it forward as the recorded messages are played out via the telephone line to the user. Detection of a second beep tone resets the control flip-flop, terminating remote playout. The device employs a single sided solid state ring detector having a transformer input circuit that presents a balanced load to the telephone line, thereby permitting ac powered operation of the device.

In this telephone answering device, the outgoing and incoming audio amplifiers are interconnected to function as a mode switching flip-flop. Remote playout is enabled upon detection of a first beep tone. This sets a control flip-flop which consists of a single operational amplifier interconnected with a steering capacitor to function as a toggleable bistable circuit. A cylindrical cam mechanism and associated control circuit are actuated by setting of the remote playout control flip-flop. These cooperate with a reel drive motor first to rewind the message tape and then to drive it forward as the recorded messages are played out via the telephone line to the user. Detection of a second beep tone resets the control flip-flop, terminating remote playout. The device employs a single sided solid state ring detector having a transformer input circuit that presents a balanced load to the telephone line, thereby permitting ac powered operation of the device.

A hot melt adhesive applicator operable at a number of selected temperatures having a portion of the circuitry for control of the applicator temperature at a point remote from the applicator body. The remotely located circuitry employs a differential amplifier and a zero crossing detector for controlling the operation of a triac which, when turned on, increases the temperature at the applicator. The operational amplifier is protected by a clamping circuit from receiving a signal, when a temperature setting is changed from a high to a low setting, that would otherwise cause the differential amplifier to provide an output required for turning on the triac which would cause a run away condition to exist.