Patent GB-765953-A (GB)
Title: Electronic transmitter, receiver and regenerative repeater for telegraph signals in a start-stop code
Inventor: SNIJDERS ANTONIE
IPC: H03K17/74
Filed: 1952-11-19
Abstract: 765,953. Code telegraphy. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Nov. 19, 1952 [Nov. 24, 1951], No. 29273/52. Class 40 (3). In apparatus for transmitting, receiving, or regenerating start-stop telegraph signals comprising a multivibrator impulse generator set into operation by a starting element persisting for a predetermined time interval to produce pulses spaced apart by intervals equal to the length of the code elements of the signal and applied to effect the cyclic operation of a distributer which determines the operational period of the impulse generator, the multivibrator comprises two valves of which the potential of the control grid one of the valves is maintained at a fixed value during the stop or rest condition and is varied by the start element of predetermined length to set the generator into operation and the fixed potential to stop the generator is reapplied to the control grid by the aid of a rectifier network under the control of the distributer and independently of the potential of the input terminal. The receiving apparatus as shown in Fig. 11 comprises a number of circuit arrangements, indicated diagrammatically, in which the input circuit VS1, distributer control circuit VS2, and memory or storage circuits GS1 ... GS5 are two-position trigger circuits described in detail in connection with Fig. 3, in which two triodes Bla, B1b are reciprocally coupled so that when B1a is conductive, B1b is cut off, and vice versa. With B1a conductive, the potential at the output terminal 9 is less (or -) with respect to that at the output terminal 4 (+) and similarly the potential at terminal 10 is - ve and that at terminal 3 is +ve. The start circuit SSS, Fig. 5, comprises a double triode, B2a, B2b such that B2b is conducting or non-conducting when a negative or positive pulse respectively is applied at 8 to the grid of the tube B2a, and the pulse generator G comprising reciprocally connected triodes is described in connection with Fig. 6 in which the anodes and grids of the triodes B3a, B3b are coupled via capacitors C1, C2. Normally, B2b is non-conducting, but the start element at input 7 of the triode B1a renders B2b conductive and after a period determined by the capacitor C1 the triodes change condition and after a further period determined by C2 return to their initial condition. The circuit arrangement IV described in connection with Fig. 8 (not shown) comprises a first triode controlled by the pulses from the generator G and a second triode controlled by the first triode forming the first of seven distributer valve circuits of which the remaining six similar circuits are formed by three double triode circuit arrangements V1, V2, V3 described in connection with Fig. 9 (not shown). In the rest or stop condition of the apparatus, the second valve of the circuit V3 is conducting so that a negative potential is applied over conductor 7 to the input terminal 7 of the circuit VS2 with the result that the voltages at the output terminals 9, 4 of the circuit are respectively positive and negative. Also the stop element at the input terminal IN renders the left-hand (l.h.) valve of the circuit VS1 conductive so that the voltage at output terminal 9 is negative and the point a is negative. When the start element is received, the l.h. valve of VS1 is made non-conducting so that the potential applied to the point a is positive and in view of the rectifiers G3, G4 the point b becomes positive and the start circuit SSS is initiated into operation. If the start element persists for a predetermined interval, e.g. 10 m. secs., the circuit of the generator G is changed over so that an impulse is transmitted to the first valve of the circuit IV which changes over and the second valve of the circuit, i.e. the first of the seven valves of the distributer, is rendered conducting and the seventh valve is made non-conducting so that a positive potential is applied over conductor 7 which renders the l.h. valve of the circuit VS2 conducting with the result that a positive potential is applied via rectifier G4 to the point b which holds the circuit SSS to maintain the generator G in operation until the seventh distributer valve again conducts at the end of the cycle. The code elements received at the input terminal IN are passed to the memory circuits GS1 ... GS5 under control of the pulses produced by the distributer and a number of rectifier networks of which the first network comprises rectifiers G47 ... G52 which are arranged to provide a path from the output terminal 4 of the circuit VS1 to the input 7 of the appropriate memory device GS1 of the series GS1 ... GS5. At 30 ms. after the beginning of the start element, the r.h. valve of circuit IV is non- conducting and the l.h. valve of the circuit V1 is conducting so that the points c, d are respectively positive and negative. If the terminal IN becomes positive and consequently the point g also positive, the point e becomes positive and f remains positive so that the trigger GS1 assumes the positive condition. If the terminal IN had been negative, the point g would become negative, e remains negative and f would become negative so that the trigger GS1 assumes the negative condition. In the transmitter arrangement, Fig. 12 (not shown), a trigger circuit which passes the signal elements to an outgoing line is under control of circuits producing an input corresponding to the code elements in conjunction with rectifier networks each controlled by impulses produced simultaneously by the successive pairs of the valves forming the distributer. As in the case of the receiving arrangement, Fig. 11, the start-stop circuit and impulse generator are controlled for starting by a pulse of 10 m.s. and, for stopping, by a circuit which is operated by a pulse of appropriate potential when the last valve of the distributer is made conducting at the end of the cycle. The regenerative repeater, Figs. 13a and 13b (not shown), comprises the complete receiver arrangement of Fig. 11, together with an additional memory circuit, similar to GS1 to GS5, included to store the stop element and a transmitting arrangement comprising rectifiers associated with outputs from the successive valves of the distributer in conjunction with the output impulses of the memory and storage circuits to control a trigger circuit to pass the regenerated code-signal elements to the outgoing line. Specifications 680,726, 765,954, [Group XL (c)], and 765,955 are referred to.