IE41962L - Pcm t.d.m. data transmission system - Google Patents

Abstract

1528900 t.d.m. data transmission SIEMENS AG 28 Nov 1975 [19 Dec 1974] 48928/75 Heading H4M In a t.d.m. system wherein a transmission path extends between end stations (not shown) via intermediate stations each containing a receiving portion Fig. 2, and a transmitting portion Fig. 1, the data being in the form of frames with frame and/or message control words acting as a monitoring signal, see Specification 1,398,961, data for transmission passing serially into shift register SRI, logic unit SL ensuring that the monitoring signal bits are interleaved, using the parallel shift register inputs into the message, there is provided a scrambler Scl {comprising a shift register with feedback from a plurality of bit positions to its input), whose pseudo-random output is combined at exclusive OR gate EXOR1 {modulo-2 adder} with the multiplex signal from the register SR1, the scrambler being reset at a given bit position {start of the message control word} of the frame, a corresponding scrambler Sc2, correspondingly reset, and exclusive or EXOR2 at the subsequent receiving portion reconstituting the multiplex signal for passage to shift register SR2 in which the message and monitor signal are separated. Should the shift register SRI cease to provide an output, the output of Sc1 is transmitted to provide a standby signal pattern. Under normal conditions of reception, logic unit EL compares the separated monitor signal with a locally generated one, the result SYN passing to a synch monitor. Should realignment be necessary, scrambler Sc2 is stopped, unit EL receiving the scrambled monitor signal for comparison with a corresponding locally generated signal. Scrambling of the transmitted signal avoids bunching in its spectral density. The scramblers may each have as many shift register stages as there are bit positions in the frame control word. [GB1528900A]