Patent GB-809205-A (GB)
Title: Magnetically controlled gating element
IPC: H03K3/38
Filed: 1956-07-10
Abstract: 809,205. Electrical digital-data-storage apparatus. RESEARCH CORPORATION. July 10, 1956 [July 27, 1955], No. 21395/56. Class 106 (1). [Also in Group XXXIX] The resistance of a 1-inch length of 0.01 inch tantalum wire 12, Fig. 3, is controlled by the magnetic field from a coil 14 of 0.003 inch niobium wire tightly wound thereon, the whole element being immersed in liquid helium. At 4.2 K., a field of about 50 gauss is sufficient to change tantalum from a super-conductive state to the normal resistive state without changing the superconductive state of the niobium. In Fig. 1, the transition temperatures of various metals are plotted against the magnetic field. The change of state of the tantalum wire may be detected by a micro-voltmeter 24 connected across the wire through which a battery 16 drives a current of about 50 m.a. Switching times of the order of 3 microsecs. are obtainable. Bi-stable device or flip-flop.-Two superconductive elements 66, 74 and 68, 72, Fig. 6, are cross-connected so that the output of one controls the other. Windings 76, 78 enable the device to be set or triggered from one state to the other. The current provided by battery 62 is limited to a value less than twice the current necessary to make one element resistive. The device cannot then be locked up with both elements resistive. Slave elements 84, 92 and 86, 90, Fig. 7, may be added so that the conditions of the master elements may be detected without disturbance. Coincidence gate, Fig. 8.-The gate consists of a tantalum wire with two control windings 102, 104. The arrangement may be such that two aiding coils are necessary to destroy conductivity. Alternatively, either of two opposing coils may destroy conductivity whilst together they allow conductivity. Memory device.-A co-ordinate array (not shown) of coincidence gates is controlled by x and y conductors. A coincidence of an x and a y marking causes a gate to operate a flip-flop like that shown in Fig. 7. Delay line.-A resistive portion can be moved stepwise along a wire 130, Fig. 11, in response to a single pulse in coil 136. When the power source 132 is switched on at 160, the current flows along wire 130. If a pulse in coil 136 destroys the conductivity of the corresponding part of 130, current flows through coil 140 and destroys conductivity in another portion and so on. After a delay at the end of the pulse the conductor 130 within coil 136 regains its conductivity and a conductive stretch of wire grows behind the resistive spot as it moves along. The resistive portions are indicated by slave elements 138, 144, &c. The stepwise destruction of conductivity can be stopped by a pulse in one of the input coils 152, 154 or 156 opposing the stepping pulse in the correspondmg coil 140, 146 or 148. Free running multivibrator or clock, Fig. 9.- Three flip-flops 110, 112, 114, of the kind shown in Fig. 7, are connected in cascade. The flipflop conductors are fed in series with current from source 116. An indicator 120 comprises a battery 124 and a microvoltmeter which are used to detect the resistance of a conductor controlled by the top right hand gating conductor of 114. The slave element coils of 110, 112, 114 are linked to the succeeding setting coils to form circuits for transferring conditions from one flip-flop to the next but the link between 114 and 118 reverses the condition. The indicator is thus changed over once per cycle. The transfer circuit includes a battery 118.