Abstract: 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.

Abstract: The invention relates to a method for transmitting data between an analog modem (3) and a remote data terminal (4). The data can be transmitted at a variable sampling rate ≧8 kHz by means of a PCM modulation method from the analog modem (3) to a subscriber line module (5) that is provided with a coder/decoder device (50) with a corresponding sampling rate via an analog data transmission line (1). From the subscriber line module (5) at least two data transmission links K1, K2, . . . , Kn to the remote data terminal (4) can be established in parallel. The data transmission capacity properties of the data transmission line (1) during establishment of the link are determined. The maximally possible number mmax of data symbols Sxy that can be transmitted per data transmission link K1, K2, . . . , Kn is determined. A certain number n of switched data transmission links K1, K2, . . .

Abstract: A method and an apparatus for the transformation of a signal on a four-wire line are proposed where the signal comprises of discrete amplitude height levels that are intended for a conversion into a corresponding analog signal with amplitude height levels suitable for a two-wire line and the analog signal is intended for a data communication unit that connects to the two-wire line and which has a predefined amplitude resolution for the analog signal. The amplitude height levels of the signal on the four-wire line are transformed in such a way in the domain of the four-wire line that the number of amplitude height levels which the communication unit can discern in the analog signal match a presetable criterion.

Abstract: 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.

Abstract: 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.