Patent GB-1268805-A (GB)
Title: Improvements in or relating to a system for the transmission of signals
IPC: H04B7/005
Filed: 1969-07-22
Abstract: 1,268,805. Multiplex pulse signalling. AUTOPHON A.G. 22 July, 1969 [26 July, 1968], No. 36811/69. Heading H4L. A continuously variable signal to be transmitted is divided into grouped sections, each section being associated with a respective frequency band, the sections being converted into frequencies within the corresponding band which are variable to represent the information content of the section. Pulse amplitude modulation systems.-A signal, Fig. 3a, is supplied to the transmitter, Fig. 1, at E1 and sampled sequentially at U.11 to U.14, Fig. 3b, under the control of a pulse generator TG1 via a counter Z1 so that capacitors C1.11 to C1.14 are charged sequentially by the corresponding samples. After each group of samples has been stored a pulse, Fig. 3c, from a multivibrator MMV1.1 operates switches U1.21 to U1.24 simultaneously to transfer the charges to capacitors C1.21 to C1.24, Fig. 3, d1, d4, e1, e4, and pulses, Fig. 3f, from a monostable device MMV1.2 then bring into simultaneous operation four oscillators G1.1 to G1.4 whose outputs lie in different frequency bands but are changed in frequency in accordance with the levels of the respective signal samples. This forms frequency stacks separated by predetermined time periods for each group of samples, Fig. 3g, where b1 to b4 represents the respective bands and f1 to f4 the frequencies within those bands, the stacks being transmitted in succession. The stores C1.1 and C1.2 alternatively may be connected in parallel and operated alternately. At the receiver, Figs. 2 and 4 (not shown), the incoming signals are recovered by bandpass filters and supplied to respective frequency discriminators whose outputs are stored in parallel form and read out serially under the control of a clock pulse generator which is phase controlled by pulses derived from the incoming signal. In a modification, Fig. 6 (not shown), a plurality of groups of samples are combined in time division multiplex fashion without any gaps in time within each frequency stack. In an alternative transmitting arrangement, Fig. 9, the incoming signal applied at E9 is sampled at U9.1 under the control of a pulse generator TG9 and stored at C9 to control the frequency of an oscillator G9.1 whose output is supplied to a modulator M9. The pulse generator controls a counter Z9 which energizes sequentially four different inputs to an oscillator G92 so that four different frequencies are produced in sequence, the duration of this sequence corresponding to four signal samples, and supplied to the modulator M9. The counter also controls a bi-stable device FF9 so that switches U9.21, U9.22 are closed alternately to supply the output of the mixer M9 to one of the two analogue stores SA S9.1 or SA 59.2 which may be in the form of a cathode-ray tube which charges and discharges capacitors arranged in the form of a divided plate, so that a complete signal stack is stored in each store. The stored signal stacks are read out alternately at L91, L92 at a reduced speed so that each stack is lengthened while the frequencies are correspondingly reduced and supplied to the output A9. Delta modulation system.-At the transmitter, Fig. 11, incoming signals at E11 are converted into delta-modulation at M11 under the control of a pulse generator TG11 and the resulting signals are supplied via gates U11.11 to U11.15 opened sequentially by a counter Z 11 to set the bi-stable devices FF11.1 to FF11.5 correspondingly, the bi-stables being reset between pulse groups by the counter Z11. Monostable devices MMV11.21 to MMV11.25 are controlled by the bi-stables through gates U11.21 to U11.25 which are opened simultaneously for a short period so that a signal of predetermined duration is supplied to control the switching of oscillators G11.1 to G11.5 according to the setting of the bi-stables to provide the frequency stacks for transmission via A11. At the receiver, Fig. 12 (not shown), the incoming signals are selected by bandpass filters under the control of timing pulses derived from the incoming signals and fed via respective demodulators to stores from which the signals are gated out between the reception of stacks to set corresponding bi-stable devices which are reset in sequence to produce a series of delta modulation pulses in their common output circuit. These pulses are integrated and filtered in known manner to reconstitute the audio-frequency signal.