Patent GB-1027081-A (GB)
Title: Improvements in or relating to a circuit arrangement for the selective energisation of inductive impedances
IPC: H03K17/81
Filed: 1963-05-09
Abstract: 1,027,081. Circuits employing bi-stable magnetic elements; diode switching circuits. COMPAGNIE DES MACHINES BULL. May 9, 1963 [June 18, 1962], No. 18471/63. Headings H3B and H3P. In a matrix store in which one of a number of column windings is selectively energized each column winding is associated with four diodes the secondary winding of a writing transformer and the secondary winding of a reading transformer. As shown in Fig. 1, a group of columns of magnetic cores 10 are magnetically coupled to a winding or conductor E1, E2 &c. each column winding being connected by means of two diodes D1-1, D1-4; D2-1, D2-4 &c. to the terminals of secondary winding SE of the writing transformer TE fed from pulse generator GE. In addition, each column winding is connected by means of two diodes D1-2, D1-3; D2-2, D2-3 &c. to the terminals of a separate secondary winding SL1, SL2 &c. respectively of reading transformer TL. If it is desired to select the first core column switch 1R1 is closed and the writing pulse generator GE is set in operation so that a voltage is set up across secondary winding SE making terminal 13 positive with respect to terminal 14. Current now passes in the direction of arrow 11 through diode D1 column winding E1, diode D1-3, switch 1R1 to terminal 14. Diode D1-4 is reverse biased by the pulse from the generator and since secondary winding SL1 has a much higher impedance than column winding E1 the current flow through diode D1-D2 is negligible and can be neglected. The current flow through the remaining column windings is also negligible due to the open switches 1R2 &c. During the reading operation generator GE is switched off and generator GL rendered operational such that a voltage pulse is set up across the terminals of each of the secondary windings SL1-SL8 resulting in terminal 15 being positive with respect to terminal 16. Current now flows in the direction of arrow 12 through column winding E1, i.e. from terminal 15 through switch 1R1, diode D1-4, winding E1, diode D1-2 to terminal 16, diode D1-3 being reverse biased and the current through winding SE being negligible. The currents flowing in the unselected windings are negligible due to diodes D2-3, D2-4 &c. being reverse biased. In the embodiment of Fig. 2, the matrix comprises N groups, each group comprising n columns of cores where N = n = 8. The writing transformer TE in this case has eight secondary windings SE1-SE8 each of which is associated with one group of columns. In addition, there are provided eight group switches IG1 to IG8 and when one group switch, e.g. IG1 is closed one of the terminals of an associated writing secondary winding is connected to common conductor 21 to which there are also connected rank switches IR1 to IRS The secondary writing winding associated with a particular group is connected across each column winding in that group and each of the reading secondary windings SL1 to SL8 is associated with eight column windings of like rank in the eight column groups. In order to select one of the sixty-four columns of the matrix a group switch and a rank switch are closed, e.g. if column winding E57 is to be selected switches IG8 and IR1 are closed. During the writing phase voltage across secondary winding SE8 causes current to flow through diode D57-1  winding E57, diode D57-3, conductor 22, switch IR1, conductor 21 and switch IG8 and during the reading phase voltage across secondary winding SL1 causes current to flow through switch IR1, conductor 21, switch 168, diode D57-4, column winding E57, diode 57-2 and conductor 23. The group and rank switches may be transistor AND gates, Figs. 3, 4 (not shown).