Patent GB-365072-A (GB)
Title: Improvements in or appertaining to distributors for telegraph or like signalling systems
IPC: H04L5/24
Filed: 1930-10-09
Abstract: 365,072. Multiplex telegraphy. STANDARD T E L EPHONES & CABLES, Ltd. and STARR, A. T., Columbia House, Aldwych, London. Oct. 9, 1930, No. 30247. [Classes 40 (iii) and 40 (v).] A distributer for telegraphy and the like utilizes a combination of two control arrangements in which a primary control successively selects a predetermined interval corresponding to a number of time elements during which a corresponding number of impulses is sequentially supplied and selectively pass to the line in accordance with the setting up of the signal contacts of the transmitters. The primary control may be effected by a brush mechanically rotated over a number of segments associated with circuits over which waves are supplied sequentially to produce the individual impulses or by a succession of control waves which are of positive amplitude during the successive predetermined intervals. In the latter case the transmitting device must be such that an impulse passes to line under control of a signal contact only when the secondary impulse is superimposed on the control wave during its operating or distributing period, i.e. during the interval when its potential is positive. In the arrangement in which the distribution of the current impulses appropriate to the time elements is effected by the operation of a mechanical distributer in conjunction with circuits which are allocated in equal numbers to the distributer segments and to which impulses under control of thermionic valves are applied, the arm b is rotated over a number of segments 1, 1<1>; 2, 21, .. a, alpha<1> with each of which is associated an equal number of separate circuits. The corresponding circuits appertaining to the segments 1, 2, .. alpha are connected, and in a similar manner the corresponding circuits of the segments 1<1>, 2<1>, .. alpha<1> are connected. The brush, which is slightly narrower than the individual segments, is rotated at an approximately uniform speed related to the maximum speed of transmission of the signal impulses. Impulse waves P1, P2, P3, .. of the form shown in Fig. 2 are simultaneously applied to the circuits formed by connecting the corresponding circuits of the segments 1, 2, .. a, 1<1>, 2<1>, .. alpha<1>. The complete series provides a set of successive impulses equal in number to the elemental impulse intervals allocated to the time during which the brush b passes over a pair of segments, say, 1, 1<1>. The impulse waves P1, P2 .. are applied simultaneously to the corresponding circuits connected to each pair of segments, but at any instant the brush will render effective only the circuits appertaining to one pair of segments. The regular sequence of unit impulses thus produced is passed to the line through the brush b in accordance with the setting up of the contacts according to the code elements to be transmitted. At the receiving end the arrangement is similar to that at the transmitter. Impulse waves P1, P2 .. are simultaneously applied to a number of receiving relays which are arranged to operate only if an incoming signal impulse is superposed on the " P " curve impulse, which in effect selects the relay appropriate to a time element. The successive " P " impulses may set up a critical condition in corresponding trigger devices which are operated only when signal impulse is simultaneously applied. Alternatively the impulses of the " P " curves may be employed to bias successive relays to a condition such that the signal impulse is able to operate the appropriate relay. The " P " curve impulses applied at the receiving end must be in step with those produced at the transmitter with the necessary allowance for transmission time along the line. The mechanical distributer, Fig. 1, may be replaced by an electrical switching arrangement which comprises a further series of impulse waves similar in general form to the curves shown in Fig. 2. The additional impulse waves are such that successive waves are of positive amplitude during the time intervals allotted to the successive pairs of segments 1, 1<1>; 2, 2<1>; ... In an arrangement of this type, shown diagrammatically in Figs. 10 and 11, switching curves S1 S2, .. having positive amplitude in successive time intervals corresponding to the sum of the time elements for the rows of contacts C1 .. C20, C21 .. C40, .. are applied at terminals D1, F1 ; D2, F2.... Simultaneously the impulse waves P1, P2, .. are applied at the terminals A1, B1 ; A2, B2; .. and in accordance with the contacts C1 .., C20 .., C40 .. set up in the open position, the amplitude of the " P " Wave is superposed on that of the "S" wave. The contact rows C1 .. C20, C21 .. C40, .. are connected at K1, L1, K2, L2, .. in the grid circuits of a number of valves Ml, M2, .. biased to remain inoperative except during the intervals when positive amplitudes of the " P " and " S " waves are superposed. In the arrangement shown, the valve M1, for example, can operate only during the interval corresponding to the contacts C1 .. C20, since during the remaining intervals of the cycle, the wave S1 is of zero amplitude. At the receiving end the relays are biased to be operated only when the signal impulses are superimposed on the combined positive amplitudes of the S and P waves. The impulse waves P1, P2, .., Fig. 2, are derived from a sinusoidal wave applied through phase-shifters to the grids of a number of valves whose plate circuits are connected in opposition so that the outputs of successive valves may in effect be subtracted. Sinusoidal current as illustrated in Fig. 5 curve (a) is applied through a high resistance Rq1 to a valve 1 and through a phase shifter PS and high resistance Rq2 to a valve 2. The individual outputs illustrated in curves (b) and (d) are subtracted to produce a wave of the form illustrated in curve (e). In the diagram, Fig. 7, showing the outputs of the valves to which the successively delayed a.c. is supplied, the curve 11 is the inverse of the curve 1, and since waves of the form represented by P1, P2, P3 .., Fig. 2, are obtained by subtracting the output of the valve 2 from that of the valve 1, and so on, the waves P11, P12, .. (not shown) may be obtained by reversing the coupling of the outputs of the valves as illustrated diagrammatically in Fig. 8 (not shown) with consequent economy of the number of valves employed. Specification 356,111 is referred to.