Sony Corporation

Other

Keizo Tsukada

Masato Yamagata

Yoshikazu Tanaka

Masato Yamagawa

A cordless telephone having a handset unit, which is powered by a battery, and a base unit for communicating with a desired party. A telephone conversation with the desired party may be interrupted by activating a hold mode. The hold mode is released by executing predetermined commands, for example, a talk request command. The hold mode is also released after a predetermined period has passed, whereupon the handset unit is placed in a relatively low power standby mode thus reducing the power consumption of the battery of the handset unit.

Cordless telephone apparatus having a low power stand-by mode and a hold

A cordless telephone having a base unit and a separate handset unit is operable in an intercom mode in which operators at the two units are in telephonic communication. If an incoming telephone call appears when the telephone is in the intercom mode, the loudspeaker of the handset unit and a ringer of the base unit both produce a ringing sound to announce the call. When one unit is then disabled by the operator thereof hanging up, the other unit is automatically connected to the telephone network line to receive the incoming call. The handset unit produces the ringing sound from its loudspeaker at a first volume when it is disabled and in a standby mode, and at a second lesser volume when it is enabled and in the intercom mode to avoid producing a loud ringing sound directly into the ear of the handset operator.

Cordless telephone

A cordless telephone has a transfer capability by which an incoming telephone call may be transferred from the base unit to the handset unit or from the handset unit to the base unit. Each unit includes an intercom key which may be actuated to place the telephone in an intercom mode wherein the base unit and the handset unit are in communication with each other while the incoming call is on hold. Deactuation of one unit in the intercom mode results in the other unit being automatically adapted to receive the incoming call. Alternatively, actuation of either intercom during the intercom mode results in both units being automatically adapted to receive the incoming call and placed in communication with each other.

A cordless telephone includes a base unit and a handset unit. When the handset unit is mounted on the base unit, an identifying code is automatically generated and stored in both units. Thereafter, when an incoming or outgoing telephone call is initiated, the two stored identifying codes are compared, and the telephone call proceeds only if the two identifying codes are identical. The new identifying code is generated as a counted value in accordance with a predetermined time following the mounting of the handset unit of the base unit. By having the predetermined time vary from telephone to telephone, the identifying codes will also vary, eliminating crosstalk interference and the risk of wiretapping.

The maximum voltage stored in a timer storage capacitor during charging is limited to a fixed level independent of battery voltage by the junction drops of a plurality of forward biased solid state devices. The discharge time of the timer storage capacitor to a predetermined triggering level is thus also independent of battery voltage. At the triggering level, control and drive circuits interrupt the supply circuit to an electric device.

Timer circuit

A power amplifier circuit is mainly composed of an amplifier including an input transistor, a driving transistor and a power amplifying transistor. This power amplifying transistor is connected at its output end to an output transformer the secondary winding of which is connected to a first adjusting means for adjusting an output impedance of the power amplifying transistor. A second adjusting means, which is interlocked with the first adjusting means, is provided on the current path of the driving transistor to adjust the value of an emitter resistance of the driving transistor, and the biasing voltage of the power amplifying transistor is obtained from the current path of the driving transistor, thus the power consumption of this circuit being reduced by the adjustment of the first and second adjusting means.

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Tokyo, Japan

Keizo Tsukada