GB1328001A - Frequency multiplex telecommunications systems - Google Patents

Abstract

1328001 Carrier multiplex systems SIEMENS AG 19 April 1971 [29 Jan 1970 (2)] 20282/71 Heading H4R In an arrangement for transmitting "video" signals over a carrier link the video signals are transmitted as a vestigial sideband signal in a band which would otherwise carry a tertiary group of 300 telephony channels. As described the original video band extending up to about 992 KHz is transposed, either in one Fig. 3 or 4 (not shown), or two, Fig. 2, modulation steps to the frequency band 812-2044, either erect (Fig. 3) or inverted (Fig. 4) with the vestigial sideband characteristic provided after the first modulation step. From this basic teritary group position the video signal can be transposed to occupy tertiary group positions in 4 MHz or 12 MHz systems in the same way as normal tertiary groups of 300 telephone channels. Alternatively, Fig. 1, the video signal can be modulated and filtered to provide an inverted vestigial sideband transmission ZF at 2916 to 4148 KHz which is used directly as the third tertiary group in a 4 MHz system with the first and second tertiary groups derived from similar intermediate signals ZF of video or telephony channels by a further modulation stage. Preferably the first transposition from video uses a carrier which is an odd number multiple of 4 KHz and derived independently from a crystal oscillator so as to have a stability of Π4 Hz while the remaining carriers are all whole number multiples of 8 KHz. The choice of carriers for the system is the subject of Specification 1,328,002.