Patent GB-853580-A (GB)
Title: Improvements in or relating to devices for indicating variations in coded information
IPC: G11C19/04
Filed: 1957-06-24
Abstract: 853,580. Circuits employing bi-stable magnetic elements. PHILIPS ELECTRICAL INDUSTRIES Ltd. June 24, 1957 [June 27, 1956], No. 19810/57. Class 40 (9). Coded information in the form of unidirectional pulses applied selectively and coincidently to a plurality of leads determines the individual directions of magnetization of a group of cores formed of rectangular hysteresis material, and any change in the code is indicated by an output pulse which is generated as a result of magnetization reversal of one or more of the cores. As shown in Fig. 1, the coded information is applied over leads 1-4 to input windings A1-A4 on cores K1-K4, and at the same time pulses from a source 6 are applied to windings B1-B4. The A and B windings act in opposition with the A windings exercizing an over-riding control, with the result that repeated applications of the same code maintain those cores associated with pulsed leads in one magnetic state, while the remaining cores are magnetized in the opposite sense. If the code changes however, the pattern of magnetization alter, and output pulses are induced in those windings N1-N4, P1-P4 which are associated with cores whose magnetic state is reversed. These windings are wound in opposition on each core and are connected to rectifiers G11-G15 Since the windings N1-N4 are connected in series and windings P1-P4 in parallel, a positive output pulse appears at terminal U whenever the coded information changes, irrespective of the combination of core reversals which takes place. Spurious outputs produced by flux excursions between remanence and saturation in the same magnetizing sense, when the code is repeated in unchanged form, are suppressed by a D.C. source V which biases the rectifiers. The separate pulse source 6 may be dispensed with by utilizing the incoming code pulses, Fig. 2, the necessary constant current through the B windings being obtained by the use of a non- linear resistor R or an output-limited triode. In a further arrangement, Fig. 3, the opposed N and P windings are omitted, and their functions are respectively performed by the series and parallel connected B and A windings which are shunted by rectifiers G11-G15. This arrangement utilizes the high impedance of a core, during the transition period when it changes state, to direct a pulse derived from the inputs or source 6 through the shunt circuits and a common resistor R20 to the output U. The number of rectifiers required may be reduced by arranging the cores so as to correspond to a matrix, Fig. 4, with cores along one diagonal omitted. Three inputs 1-3 are provided in this embodiment, each being applied to a row and to a column of cores over series-connected A and B windings. As before, the A and B windings act in opposition and a core is acted upon by an input pulse passing through its B winding only if no input is effective in its A winding. Opposed N and P windings are also provided, the correspondingly lettered windings on each side of the diagonal being connected in series with a rectifier G21-G24. As before, a change of code is indicated by an output pulse at U. In a modification, Fig. 5 (not shown), one rectifier may be omitted by connecting all the P windings in series. A further arrangement, Fig. 6, utilizes a single winding P<SP>1</SP> on each core in place of separate P and N windings, the P<SP>1</SP> windings on each side of the diagonal forming a closed series circuit, in conjunction with resistors R41-R44, which is associated with rectifiers G41-G44 so as to provide an output at U irrespective of the direction of the induced current.