GB710205A - Improvements in or relating to carrier-wave telephone systems - Google Patents

Abstract

710,205. Multiplex systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Feb. 20, 1952 [Feb. 23, 1951], No. 4499/52. Class 40 (4) In a carrier multiplex system, the frequencies of carriers used for pilot signals are higher than the frequencies in the basic group of intelligence channels formed by the first stage of frequencytransposing modulation, lie between the upper and lower limits of the total band which comprises the frequencies of all the transposed intellgience channels transmitted from sending to receiving station, and do not fall within any of the bands occupied by the said transposed intelligence channels. As shown, twelve 0-4 kc./s. intelligence channels are formed into a basic group 1 by means of channel carriers having frequencies of 12, 16, ..., 56 kc./s. Group carrier frequencies of 300; 348, ..., 492 kc./s. are then used to form five groups. into a basic super-group 2, and sixteen such super-groups are arranged in a basic hypergroup (Fig. 1c) in such a way that the supergroup carriers fall in the centres of the gaps between the super-groups and so may be used for pilot signals. The super-group carries frequencies and other pilot carrier frequencier are all multiples of 288 kc./s., and all the carriers required are derived from a 144 kc./s. oscillator by means of frequency division and/or multiplication and/or mixing, Fig. 2 (not shown). If a 124 kc./s. COIF oscillator is to be used, this may be synchronized by mixing the 144 kc./s. oscillations with the 20 kc./s. channel carrier.