Patent GB-767686-A (GB)
Title: Improvements in or relating to trigger circuits
Inventor: GRAYSON HARRY
IPC: H03K23/76
Filed: 1953-02-17
Abstract: 767,686. Electronic counting apparatus. STANDARD TELEPHONES & CABLES, Ltd. Feb. 17, 1953, No. 4381/53. Class 106 (1). [Also in Group XXXIX] A pulse counter comprises a chain of magnetic trigger circuits 1a, 2a, &c., 1b, 2b, &c., Fig. 3, driven by a frequency doubler DL and a frequency doubler inverter DL1. The doubler DL and the inverter DL1 convert a train of pulses o, Fig. 4, of frequency f applied at P into pulse trains a and b of frequency 2f. Each b unit comprises a second harmonic transformer, Fig. 1, which is triggered from one stable state to another by a positive pulse at K, when the primary windings α, α<SP>1</SP> are fed with 50 kc/s. at A. Point G is connected to 10 volts positive battery. In the first state, there is no direct current flow in secondary windings #, y since with no control potential at K, rectifier r1 is biased sufficiently to block the residual weak harmonics. A positive potential at K energizes winding y and produces sufficiently strong harmonics to overcome the bias on r1 and to maintain y energized. In this second state, a neon tube N indicates that the winding is ener. gized. The transformer returns to the first state when the high-frequency supply at A is momentarily interrupted. The rectifier r1 and the bias G are reversed in each a unit so that it responds to negative pulses. Each a pulse is fed to all the trigger circuits 1a, 2a, &c. but triggers only that one, say la, primed by the last triggered circuit nb. Circuit 1b is primed by 1a and is triggered by the next b pulse. In Fig. 6, showing circuits 1a, 1b and parts of 2a, nb, the primary windings and the cores are not shown. The a and b pulses are fed to the primary windings. Circuit 1a is primed when a positive voltage through R in nb energizes y. When the a pulse is received, the second harmonics in # open rectifier Da and the circuit is now " On." Circuit 1b is primed by current flowing in y in 1b but the circuit remains " Off until the a pulse ends to return 1a to the " Off " state and a b pulse begins. The delay circuit RC<SP>1</SP> in 1a enables the winding y in 1b to remain energized until the circuit is triggered by the b pulse. Each circuit of the series 1a, 2a, &c. is provided with a registering device M1 and, if n is 10, one of the devices may operate a tens counter. A trigger pair of second harmonic transformers comprises secondary windings y1, #1 and y2, #2, Fig. 8, the primaries not being shown. Points J1 and J2 are at the same potential and in one state, with the first transformer " On " and the second transformer " Off," current flows from J 1 to ground through rectifier D2. Winding #1 produces harmonics of sufficient strength to raise the potential at U to block rectifier D1 and to maintain transformer 2 in the " Off " state. The " On/Off " state of the pair of transformers could be reversed by momentarily energizing y2 but the same effect is achieved by a short pulse at P. The pulse blocks both D 1 and D2 and if the pulse is short, the rise of current is quicker in the last " Off " circuit than in the last " On " circuit as C<SP>1</SP>2 will delay the potential drop in R<SP>1</SP>2. Each successive pulse reverses the conditions of the two transformers. Specifications 724,537, [Group XXXV], and 767,687, [Group XXXIX], are referred to.