Patent GB-908167-A (GB)
Title: Improvements in or relating to devices for shifting a block signal to a given mean phase relatively to the pulse instants of an incoming pulse sequence
IPC: H04L7/02
Filed: 1961-02-22
Abstract: 908,167. Type-printing telegraphy. PHILIPS ELECTRICAL INDUSTRIES Ltd. Feb. 22, 1961 [Feb. 22, 1960], No. 6491/61. Class 40 (3). [Also in Group XL (c)] The invention provides an apparatus for shifting a block pulse to a given mean phase and for holding it therein with respect to the pulse instants of an incoming pulse sequence. The incoming pulses may be telegraph pulses which are to be sampled at their centres, the sampling pulses being derived from the block signal. The method of sampling is not described. In the description which follows, lower case reference letters indicate waveforms illustrated in Fig. 2. General arrangement. Fig. 1.-Telegraph pulses d are differentiated and rectified, the resulting pulses e being passed to the apparatus of the invention. A clock pulse generator 1 gives waveforms a and c which have a repetition frequency which is a multiple of that of the incoming telegraph pulses, and which are interleaved. These pulses are fed to a block signal generator 2, pulses c also feeding a counting device 3. Counter 3, on reception of a pulse e, counts a certain number (preferably an odd number, e.g. nine) of the pulses c, and allows this number of pulses f to be fed to a signal generator 4. By the use of bistable circuits, the block signal generator 2 derives from the pulses fed to it a block signal b which forms a second input to the generator 4. The generator is driven stepwise as at k in one direction or the other dependent on the value of the block pulse b, and produces a first correction pulse h when it reaches an extreme position in one direction and a second correction pulse i when it reaches an extreme position in the other direction. It will normally be several incoming signals d before a correction pulse issues. The correction pulses act on the block generator 2 such that pulses h cause the block pulses to be delayed, while pulses i cause them to be advanced. Sampling pulses g, dependant on the position of the block pulses, are obtained from the generator. Block signal generator, Figs. 4 and 5.-This unit comprises a pulse gate, Fig. 4, and a counting circuit, Fig. 5. The pulse trains a and c, and the correction pulses h and i are fed to the pulse gate as indicated. In the absence of correction pulses bistable unit 38 is such that gate 35 is open and gate 36 is shut, while a second bistable unit 39 maintains gate 37 shut. Pulses a therefore pass to the output 30. Receipt of a pulse h causes gate 35 to open and gate 36 to shut. The pulse of pulse train a occurring when this condition obtains can not pass to the output 30 but resets unit 38. Further pulses a are not blocked, so that pulse train at 30 is as at a but with just one pulse omitted. On the other hand, receipt of a pulse i opens gate 37 which allows a pulse of train c to pass to the output 30 and also to reset unit 39. The pulse train at 30 in this case is as at a but with just one pulse interleaved. The pulses at 30 feed the counting circuit, Fig. 5, which comprises a chain of bistable units 40-43, and undergo transformation through the stages a<SP>1</SP>, a<SP>11</SP>, a<SP>111</SP>, b. A gate 47 is opened by the pulses b, which then passes one of the outputs of unit 42 to the output terminal 32. Signal generator 4, Fig. 1.-This unit, fully described with reference to Figs. 7-10 (not shown), comprises bistable circuits and gates in cascade, whereby the correction pulses h, i are generated. General.-It is stated that the component parts of the apparatus of the invention need not be electronic; mechanical and electromechanical devices being mentioned briefly.