Patent GB-456828-A (GB)
Title: A magnetically operated amplifying and control system
IPC: H03F9/02
Filed: 1935-05-16
Abstract: 456,828. Distant - control systems; road signals for controlling traffic. FITZGERALD, A. S., 433, Warwick Road, Wynnewood, Pennsylvania, U.S.A. May 16, 1935, No. 14411. Convention date, July 23, 1934. [Classes 40 (i) and 118 (ii)] [See also Group XXXIX] An electromagnetic amplifying and control device comprises a core having an alternating current winding 2 and a direct current saturating winding 3 energized by current proportional to that in winding 2, said windings controlling the energization of a load circuit 7 in accordance with the magnetic condition of the core as determined by a further winding or windings. The D.C. in winding 3 is derived by rectification at 6 from A.C. in winding 2 and the load circuit may be arranged to be energized by D.C. (as shown) or A.C. The magnetic condition of the core is determined by further D.C. saturating windings 4, 5, the current through 4 being adjustable and adapted to be reversed. The effect of winding 4 alone will first be considered. The relationship between the current I in the load circuit 7 and the voltage supplied at 9 follows the curve C or D, Fig. 4, in accordance with the direction of current supplied to winding 4. This current may only be supplied momentarily by closing switch 14 or 15, the residual magnetism determining whether the load current shall be according to curve C or D respectively. If 14 is pressed, the load current will be consistently large whenever the supply is connected up at switch 10, whereas if 15 is pressed, the load current will be consistently small, and the effect is obtained by a relatively small supply of energy to winding 4. This applies to cases if applied A.C. voltage does not exceed V<1>. For increased values of applied A.C., the circuit operates in a similar manner if D.C. is applied to a third winding 5 which opposes winding 3, and the load current can be varied either by adjustment of the current in 5 or reversal of the current in 4. The change-over from small to large load currents may be effected with delay action if the magnetic action of winding 4 is sufficiently small. The load may be a motor or a lighting circuit. In the arrangement shown in Fig. 7, a second saturable core device 20 is connected in cascade for amplifying purposes, but the current in winding 40 (corresponding to 4) is not reversible. This Figure also shows the application of the invention to controlling the load circuit by a moving object 28 in conjunction with light sources 26, 27 and photo-electric cells 23, 24. The normally balanced bridge 21 ... 24 unbalances in opposite directions as the object 28 intercepts the sources 26, 27 in succession, thereby causing current reversal in the control winding 4. The load may be a railway crossing alarm and 28 a train. Other methods of control may be used, for example, the cells may be operated from a single light source by moving a shutter, or the cells may be controlled by light of different colours by using separate sources or a single source with filters. This may be applied to the on and off switching of aerodrome landing lights by different coloured beams from aircraft. A bridge arrangement unbalanced by acoustic or wireless signals is described, and the bridge may comprise non-linear resistance elements so that it is unbalanced by signals of predetermined duration or intensity.