Patent GB-782597-A (GB)
Title: Improvements in or relating to magnetic core storage devices
Inventor: SPENCER ARTHUR JAMES
IPC: G11C11/06
Filed: 1955-04-20
Abstract: 782,597. Electric digital-data-storage apparatus. BRITISH TABULATING MACHINE CO., Ltd. Feb. 22, 1956 [April 20, 1955], No. 11405/55. Class 106 (1). Magnetic core storage arrangements.-Data storage apparatus includes two or more magnetic storage cores, each switchable to either of two magnetic states, means for switching the cores individually from an initial state to the alternative state, a resetting winding on each core, a reset circuit adapted to apply a current to the resetting windings in parallel, the current flowing through the windings tending to switch the cores to the initial state, but being insufficient to switch any of the cores to the initial state if one or more of the cores is already in the initial state when the current is applied and means for producing an output signal from a core when it is switched. As shown in Fig. 1, two cores 1 and 2 have resetting windings 3, 5 connected in parallel and series-connected output windings 4, 6. The windings 3, 5 are supplied from a line 10 through condenser 9, resistance 8 and contacts 7. When the contacts 7 are closed, a charging, current for condenser 9 flows through windings 3, 5, tending to reset the cores. A shunt resistance 11 discharges the condenser after the contacts 7 open but its resistance is high compared to the impedance of the condenser. If only one of the cores, say core 1, has been switched from its initial state to an alternative state, upon contacts 7 closing, the charging current for condenser 9 initially is shared equally between the windings 3, 5 and the current flowing in. coil 3 begins to cause a reversal of the flux until the steep part of the hysteresis loop is reached. The high rate of change of flux in the core causes the impedance of winding to rise steeply so that most of the current now passes through the parallel winding 5 which acts as a low impedance by-pass. By this time the condenser is fully charged and the current ceases, the winding 3 having had insufficient current to reset the core 1 and core 2 being already in the initial state. Since neither core is altered in state, substantially no output is obtained on windings 4, 6. The circuit may include more than two cores the constants of the circuit being such that no output is obtained when any core is unset (as 2) and when they are all in the set condition they are all switched to the initial state so as to provide an output on the windings 4, 6, &c. In the form of Fig. 2, this principle is applied to a fourcore store for the four code components of a decimal digit sensed from a record card. A digit is represented by a perforation at a selected column position on a card and the value of the perforation is given by the index time at which it is sensed. The digits are entered into the store in a four component code, six digits 9-4 being represented by combinations of two components (e.g. 9=AB, 8= CD, &c.) and the remaining four digits 3,2,1,0 are represented by single code components (3=A, 2=B, 1=C, O=D). Each of these.code components is stored on the corresponding core. Read in.-Each core has three windings 13, 14, 15, windings 13 being connected in series between supply line 10, resistor 17, contacts 16 and sensing brush 18. Windings 15 are connected between supply line 10 and brushes 21A, 21B, &c. of a commutator 22. When contacts 12 are closed and the brush 21A is on the conducting segment of a commutator the winding 15A is energized. When brush 18 senses a hole windings 13 are energized. The value of resistors 17 and 20 is such that neither winding 13 or 15 alone can drive the core to the alternative state but when they are both energized together the core is switched. The windings 15 are selectively energized according to the code so that for example at " 8 " digit time windings 15C and 15D are energized. If there is a perforation at " 8 " digit position the windings 13 will also be energized causing cores C and D to be switched. Read out.-The cores are sensed for each digit in turn under the control of a read out commutator 24. For digits 9-4 the cores are sensed in pairs while for digits 3-0 they are sensed one at a time. By closing contacts 25 windings 14 are connected to brushes 23A, 23B, &c., co-operating with commutator 24. The other ends of windings 14: are connected through the resistor 8 and condenser 9 to line 10. The commutator energizes the windings 14 according to the code pattern adopted. At "9" digit time windings 14 of cores A and B are energized. If both cores are set they will be switched back to the initial state giving an output from windings 13 on line 26. Cores C and D are then sensed for a stored " 8 " and so on. When the cores are sensed for "3"  only winding 14A is energized and an output is obtained if core A is set. It is necessary to sense the combination code digits 9-4 before sensing the single code digits 3-0 because otherwise one of the cores would be reset and a false digit would be read out. Repeated read-out.-Cores are reset by the reading operation but it may be desirable to read-out the stored data more than once. To do this the cores are set again immediately after being reset. For this purpose one side of resistor 17 is connected by line 26 to the anode of a gas-filled triode which is fired by the output pulse. The anode current energizes the windings 13 so if the contacts 12 are closed and contacts 25 are opened the cores are set under the control of commutator 22. The commutators are synchronized so that the cores set by the fired triode are those that have just been read out. Other codes may be used. Specification 769,478 is referred to.