Siemens Aktiengesellschaft

Gerhard Kunde

Siegfried Schoen

Herwig Trimmel

A telephone subscriber station has a base set and a cordless hand set. The transmission between the base and hand set occurs by way of infrared transmitters and infrared receivers. Pulse phase modulation who is particularly suited for the speech transmission. Various functions are remotely controlled from the cordless hand set by the transmission of special characters. The special characters are transmitted as pulse sequences having differing frequencies. Thereby, a specific frequency is assigned to each special character. A call device comprises keys and a controllable pulse generator. A frequency recognition circuit is provided in the receiver at the base set and assigns the received pulse sequences to the special characters and has corresponding control functions. A monitoring circuit monitors the synchronization between the hand set and the base set and disconnects the telephone connection given a transmission which is disrupted over a longer interval.

Telephone subscriber station

A multifrequency signaling method is provided between a cordless hand set and a base set which normally operates with audio frequency/pulse phase modulation and pulse phase modulation/audio frequency conversion. The cordless hand set is provided with a dialing device and a frequency generator for providing frequency combinations corresponding to dialed digits or special characters. In the base set a monitoring circuit monitors the existence of optical transmission channels between the hand set and the base set and causes disconnection after a loss of such channels for a predetermined interval. The base set also includes a converter for converting the multifrequency signals to dial pulse signals and a special character evaluation circuit for providing corresponding signals to control various functions such as signaling a secretary, through connection of a call and disconnection of a call.

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Munich, Germany

Gerhard Kunde