Patent GB-941091-A (GB)
Title: Improvements in or relating to electric circuits employing magnetic core structures
IPC: G11C19/06
Filed: 1960-05-25
Abstract: 941,091. Magnetic pulse storage apparatus. WESTERN ELECTRIC CO. Inc. May 25, 1960 [June 4, 1959], No. 18455/60. Heading H3B. [Also in Division G4] A magnetic structure for pulse storage or code conversion is formed of material having stable remanent flux states, and comprises a plurality of counting legs 11 1 - 11 0 , Fig. 1, linked by side rails 12, 13 to a drive leg 14, the magnetic state of the drive leg being reversed in steps by successive pulses in a drive winding 16 so that each counting leg in turn has its magnetic state reversed. As each driving pulse is required to reverse the magnetic state of only a single counting leg, its duration is controlled by the output induced in a step winding 20 on all the counting legs. This action is ensured by the provision of guard legs 11g intermediate the counting legs and by a bias winding 15 which is energized at the same time as the drive winding and encircles the whole of side rail 12 except for the portion between the drive leg and the first counting leg. The device is constructed so that the drive leg and side rails have a cross-section at least equal to the sum of the cross-sections of the counting legs, and operates on the principle that the order of flux reversal of the counting legs is determined by their respective path lengths from the drive leg and by the degree of bias. The structure may be channel-shaped as shown in Fig. 7 to provide the required small cross-sectional areas of the counting legs. The Fig. 1 device operates as a decimal serial to 2-out-of-5 parallel converter, and is controlled by the circuits in Fig. 2 which comprise drive 30 and reset 60 mono-stable transistor pairs and a pulse shaping amplifier 50. Of the transistors 31, 32 and 61, 62 in the circuits 30 and 60, the output transistors 31, 61 are normally non-conducting. Initially, the magnetic structure is in a reset state in which the counting legs are all magnetized in the same direction. When the first decimal pulse is applied from a source 80 to circuit 81, transistor 32 is cut-off and transistor 31 becomes conductive for a limited period by virtue of the capacitor coupling 38. A pulse is thus applied to the bias and drive windings 15, 16 over leads 34, 30<SP>1</SP>, the drive winding voltage being limited by a biased diode 48. As a result the drive leg flux commences to reverse its state, and the first counting leg 11 has its magnetization reversed since this leg provides the shortest flux path. This reversal induces a pulse in step output winding 20 which passes over lead 50<SP>1</SP> to the amplifier 50 which comprises a transistor 51. Here the pulse is converted to a rectangular form 55<SP>1</SP>, and subsequently it is differentiated by a capacitor 58. The second peak of the differentiated pulse 55<SP>1</SP>d causes transistor 32 to conduct, and transistor 31 then cuts off prematurely to terminate the drive and bias pulses. Any overspill of flux from the first counting leg before termination occurs is taken up by the first guard leg 11g. When the second input pulse is transmitted from 80, the flux in this guard leg is completely reversed and counting leg 11 2  then reverses its state. As soon as this happens an induced step output pulse terminates the drive. Counting continues in like manner until the total decimal input is registered. The counting legs are provided with code output windings 21 which are connected so as to provide 0, 1, 2, 4 and 7 outputs to a utilization circuit 83, these outputs being obtained when the flux of the magnetic structure is restored to its initial state by a pulse in a reset winding 17. This operation is effected by a reset pulse applied to terminal 77 which triggers the monostable circuit 60. A modified structure which functions as a 2-out-of-5 parallel to decimal series converter is shown in Fig. 5. The coded inputs are applied over leads 1, 2, 4 and 7 to code windings 98 distributed over counting legs 91 1 -91 13 , a counting leg and adjacent guard leg if encircled by a code winding being magnetized in opposite senses. The code input 0 has no windings on the device. The structure is driven as previously described by a monostable drive circuit 100 which in turn is controlled over an amplifier 110 and has a clock pulse input 112. Each clock pulse causes the drive mono-stabler to partially reset the state of drive leg 94 which was incompletely reversed by the flux reversals in the coded counting legs, the restoration of state progressing until the flux has passed along the counting limbs from left to right to the first position at which a reversed state counting leg is found. At this point the reversed flux is restored to normal and the driving pulse terminated over amplifier 110 by an output pulse induced by the counting leg in winding 97. This output pulse constitutes a decimal output pulse at terminal 107. Thus, with a coded input 4, counting legs 91 4 -91 7  are reversed and the first clock pulse causes the core flux to extend to and include leg 91 4 . The next clock pulse resets leg 91 5  and so on to leg 91 7 . The flux of the structure is then in its initial state. A serial in-serial out binary store is shown in Fig. 6 which is modified by the addition of a second drive leg 124. The input signals are applied by a source 140 to an input drive circuit 139 in synchronism with clock pulses at terminal 136, the drive circuit being as described in Fig. 2. Each counting leg is 125 1 , 125 3  ... except the last leg 125n is initially biased by windings 132, 133 which are energized over a multiple terminal stepping switch 135. Each binary input signal appears as the presence or absence of a drive pulse in winding 126. The first clock pulse causes registration in the last counting leg 125n, the magnetic state being reversed by a drive pulse if the input signal is a binary one. The second clock pulse steps the switch 135 so that bias is removed from winding 132 and the second binary signal is registered in leg 125 3 . Bias winding 133 is disconnected by the switch for the third input and registration takes place in leg 125 1 . The stored information is read-out by clock pulses applied over an output drive circuit 141 to a drive winding 127 on the second drive leg 124, reading out taking place in the manner previously described from the adjacent counting leg 125n and proceeding to legs 125 3  and 125 1 . The serial output pulses are produced in an output winding 130. Duration control of each driving pulse is effected by signals induced in input step windings 129 and output step windings 129<SP>1</SP>. Resetting of the structure to an initial state is carried out from the input drive circuit 139 over a winding 128. The use of alternate guard legs such as 125 2 , 125 4  in Fig. 6 is avoided in the structures shown in Fig. 7. Here one structure 150 comprises counting legs only, the other structure 160 guards legs only. The drive winding 166 is common to both structures and the output winding 168 is on structure 150 alone. A graded bias arrangement is used, the bias winding 165 being passed between the counting and guard legs so that the first counting leg is unbiased, the first guard leg is biased by one turn, and the remaining counting and bias legs are biased each by two turns. Thus adjacent guard and counting legs are biased respectively to different extents. Specification 919,235 is referred to.