Patent GB-703578-A (GB)
Title: Means for evaluating and coding an electrical quantity
IPC: G08C19/28
Filed: 1951-10-05
Abstract: 703,578. Electric selective signalling. GENERAL ELECTRIC CO., Ltd., SMART, N. C., and FIELD, R. W. G. Aug. 21, 1952 [Oct. 5, 1951], No. 23265/51. Class 40 (1). A counting chain comprising a series of twostate-units e.g. relays or gas discharge tubes, adapted to be operated in sequence by an impulse timing train, is also used to store a binary code signal by holding certain units operated and releasing others, after their ' counting functions have been performed. The invention is described as applied to a modification of the telemetering arrangement disclosed in Specification 694,907 in which the memory relay chain is dispensed with and the counting relay chain is used also for memorizing the denominational steps corresponding to the value being transmitted. As shown Fig. 1, a current proportional to the variable whose magnitude is to be encoded, exerts a torque on a coil CM1 of a comparison meter CM, tending to close contacts CM3 in opposition to the counter torque produced thereon by a coil CM2. When a reading is to be transmitted a start relay ST is momentarily energized to zeroize the counter and memory relay chain A -G and to energize a relay STA, which locks, deenergizes ST and at STA3 energizes a relay N which interacts with the slow-tooperate and slow-to-release timing relays X, Y to energize the relays A-G of the relay chain in succession. These relays are operated over their left hand windings via the impulsing contacts X2, Y2 and lock over their right hand windings. At the first step, when relay A operates, a direct current corresponding to ¢ maximum torque exerted by the originating coil CM1, is fed over contacts A4 to the comparator coil CM2, and if this current is insufficient to balance the originating current, a slow-torelease relay H is energized when both timing relays X, Y are operated, and permits relay A to remain locked. If, however, the current in the comparator coil CM2 overbalances the originating current in coil CM1, the relay H is not operated and, when relay X releases to operate the next relay, B, in the chain, the centre-reverse winding of relay A is energized causing relay A to relapse. As in the above mentioned Specification, the successive energization of the counting relays A-G increases the comparator current in coil CM2 over the contacts A4, B4-G4, by ¢, “, #, -1/128 of the "maximum" torque current, respectively. The torque comparison is made at each code step, as above described, and, depending on whether relay H is operated or not, the'associated counting relay remains locked for " underbalance " and relapses to remove the corresponding increment of counter current from the coil GM2 for "overbalance." This is effected after the succeeding counter relay has operated but before the next torque comparison is made. At the end of the counting cycle a relay R is operated, which locks, and releases STA slowly to stop cycling of the impulsing relays N, X, Y. The relays of the counting chain which are now operated (or not operated) represent the value of the originating current in binary form and over contacts A5, B6-G6, this binary value is transmitted. The binary reading is held on the counter-memory chain A-G until the start relay is operated to initiate a further reading when all the operated relays A-G, R are zeroized. Modifications. The comparison current in coil CM2 may be varied by fractional subtraction instead of fractional addition and the binary value may be transmitted by sending a signal from each operated or unoperated relay in the memory chain.