Siemens Aktiengesellschaft

Gerald Hoefer

Michael Alger-Meunier

Yousif Ammar

Dieter Brueckmann

A method is disclosed for generating a PCM code set for encoding data by a PCM encoder in a data transmission system having a digital modem with a PCM encoder, a digital signal transmission path, an analogue signal transmission path with a central office line interface portion, and an analogue modem. The method includes the step of determining a minimum signal level distance between adjacent PCM codes of the PCM code set, the minimum signal level distance enabling discrimination by the analogue modem. Then a line interface attenuation of the central office line interface portion is determined. Finally, the PCM code set on the basis of a power limit computed by adding the line interface attenuation to a central office line interface power limit is generated. The invention further relates to an analogue modem to be operated in such a data transmission system.

Method of and apparatus for generating PCM code sets

An apparatus transmits digital signals between a higher-ranking station and one or more subordinate stations through transmission devices. A signal transit time is automatically measured in the transmission devices, differences in transit time are automatically compensated for and useful signals in the various subordinate stations are automatically synchronized with one another.

Apparatus for compensating for signal transit time differences of digital transmission devices

A digital message switching system includes at least one digital message switching unit and a plurality of subordinate units each being coupled to the respective switching unit through a respective transmission link. In order to signal a request of a subordinate unit to transmit, that unit first sends at least one message of meaningless content to a higher-ranking unit and only then sends messages of meaningful content.

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Langerringen, Germany

Gerald Hoefer