Patent GB-812619-A (GB)
Title: Improvements in or relating to electrical circuits employing ferroelectric condensers
IPC: H01G7/06
Filed: 1956-06-05
Abstract: 812,619. Pattern-movement stepping registers. WESTERN ELECTRIC CO. Inc. June 5, 1956 [June 7, 1955], No. 17338/56. Class 106 (1). [Also in Group XXXIX] A binary storage unit for a shifting register comprises a ferro-electric condenser having a dielectric of barium titanate or guanidinium aluminium sulphate hexahydrate which is connected in series with a pair of opposed diodes, one or both of the diodes being of the Zener or saturation type which has the property of conducting in the normally non-conductive direction when subjected to voltages above a certain threshold value. The Zener diodes are represented in the drawings by filled arrows. In one arrangement, Fig. 1, a single ferroelectric condenser 10 is connected in series with a Zener diode 11, an opposed ordinary diode 12 and a resistance 13. A binary one is recorded by the condenser when partial-storage negative and positive pulses 19 and 23 are applied simultaneously by respective pulse sources 16 and 21, the combined voltage exceeding the threshold voltage of a Zener diode 26. The condenser is restored to the binary zero state and an output pulse developed across resistor 13 by a positive sensing pulse 18 from source 16 which is barred from the circuit of pulse source 21 by an ordinary rectifier 25, the amplitude of the sensing pulse being sufficient to breakdown Zener diode 11. A shift register circuit is shown in Fig. 3 in which each stage comprises two Ferro-electric condensers 31A, 32A connected in series with an ordinary diode 12 and an opposed Zener diode 11, successive stages being coupled by an ordinary diode. In operation, a binary one is initially registered in condenser 31a by a negative pulse 35 on shift lead 17, the associated diode 34 being grounded. This registration is transferred to condenser 31B in the next stage by applying a positive pulse 36 and a negative pulse 35, the effect of pulse 36 being to reverse the state of 31A and establish a like condition in 32A, while pulse 35 reverses the state of 32A and 31B over a transfer circuit comprising diode 34. As before, an output is obtained across the associated resistor 13. In a modification, Fig. 4, a shifting register is provided with parallel inputs 40-43 and parallel outputs 15, an ordinary diode 44 and an opposed Zener diode 45 connected in each input lead functioning as open switches except when positive inputs in excess of a threshold value are applied. It is stated that Zener diodes 11 may alternatively be connected in series with diodes 34. A code converting arrangement is described. Fig. 5, for changing dial pulses to a two-out-of-five code. As shown, a train of dial impulses is applied to terminal 50 and is combined with a bias potential 52 so that an effective squarewave signal of alternate negative and positive pulses acts on the two shift registers portrayed. A relay 53 operates in the interdigital intervals to set a binary one in a ferro-electric condenser 55 and at the same time clears the registers by connecting up a pulse source 56. When a pulse train is received, relay 53 falls back and the polarized condenser 55 sets the upper condenser in the first stage of each register over a circuit comprising ordinary diodes 58A, 58B and opposed Zener diodes 59A, the condenser 55 being sufficiently large in relation to the other condensers to perform the dualsetting operation. This binary one setting is shifted along each register in accordance with the number of pulses received, and output pulses are produced at appropriate code-terminals " 0 " OUT ... " 7 " OUT when relay 53 closes for the interdigital interval and commences to clear the registers. A further application concerns selective ringing on a party line, each subscriber being allotted a particular code in an impulse train of five pulses formed of positive and negative pulse combinations which is followed by a positive end of signal pulse. The selective ringing arrangement shown in Fig. 6 responds to the code 100101 which is applied to a shifting register and to a pulse generator 62 by way of an input terminal 60. A train of negative square-wave ulses is produced by generator 62 which perform the shifting operation in the register after conversion by a resistance-capacitance circuit 68, 69 into alternate positive and negative spikes. After the fifth positive spike the code pulses, if applicable to the register, are stored in the fifth and second stages, and blocking output pulses from these stages will be applied simultaneously to diodes 71, 72 of an AND gate 74. At the same time the end of signal pulse is applied directly to diode 73 and the flow of current from a source 76 is diverted to a ringing oscillator 77 to call the subscriber required. At the same time the oscillator transmits a clear signal to the register. A multi-condenser ferro-electric store suitable for a shift register is described, Fig. 7, which comprises a ferroelectric slab 85 having a pair of parallel electrodes 82, 83 on one face and a number of short electrodes 86, 87 on the other face, two groups of condensers being formed by the electrodes 82, 86 and 83, 87 respectively. It is stated that tapered electrodes may be used so that the capacitance of the stages are graded with the largest capacitor comprising the last stage of the shift register. Where both opposed dioes such as 11 and 12 are of the Zener type, it is suggested that they may be constituted by a single unit as in a double anode fused junction silicon diode. Specifications 697,880, [Group XXXVI], 717,104, 719,288, 810,451, [Group XXXVI], and U.S.A. Specification 2,675,396 are referred to.