Patent GB-841844-A (GB)
Title: Improvements relating to chain circuits such as are used for storage purposes in automatic exchange systems
Inventor: WARMAN BLOOMFIELD JAMES
IPC: H03K23/82
Filed: 1955-11-04
Abstract: 841,844. Multi-stable-state circuits. SIEMENS EDISON SWAN Ltd. Oct. l 1956 [Nov. 4, 1955], No. 31633/55. Class 40(6). [Also in Group XIX] A chain circuit comprises serially connected link circuits or stages each comprising an input capacitor and a two-terminal trigger device (i.e. a device whose voltage/current characteristic exhibits a negative resistance region), a first terminal of the capacitor in each stage being connected to a first terminal of the trigger device, and also to a second terminal of the trigger device of the immediately preceding stage, if any, and a marking condition constituted by a charge on an input capacitor is stepped along the chain from one stage to an immediately adjacent stage by applying a transfer voltage to the second terminal of the input capacitor of one of the two stages to trigger one of the trigger devices, the consequent current flow through this device causing the charge to be transferred from the one input capacitor to the other, rectifiers or biasing means ensuring that the stepping takes place in the requisite direction along the chain. The trigger devices may be transistors or, as shown, cold-cathode gas-filled diodes. In the circuit shown in Fig. 1, input capacitor 1C1 is initially charged to voltage V ST  through a switch 1S1. When this capacitor subsequently receives on its second terminal from rotary switch 1S2 a voltage Vp = V ST  + V M  (where V M  is the maintaining voltage of the gas-filled diodes), a gas-filled diode 1D1 is triggered, and current flows through rectifier 1MR1 to charge up capacitor 1 C2 in such manner that when the diode is extinguished the whole of the charge (V ST ) has been transferred from 1C1 to 1C2. Similarly, as the switch 1S2 steps on it applies the voltage Vp to 1C2 to cause the charge to be similarly transferred to 1C3 and so on, the circuit being ring-connected so that the charge is returned from capacitor 1C4 to 1C1. It is shown in the Specification that the chain circuit causes the capacitor charges to remain substantially constant, even if e.g. voltage V M  varies. The rectifiers such as 1MR1, which ensure that stepping of the charge take place in the required direction, may be replaced by a double rotary switch coupled in each position to a pair of adjacent stages. Various other modifications are described e.g. the capacitors may be shunted by leak resistors; and a pair of lines which receive positive pulses alternately may be connected to odd- and even-numbered capacitors respectively. As shown in Fig. 5, a single input line which receives positive and negative pulses alternately is connected to capacitors 5C2, 5C4 the other capacitors 5C1, 5C3 having their second terminals connected to earth. A positive pulse acts as previously described, but a negative pulse acts to "pull" a charge to the capacitor (e.g. 5C2) to which the pulse is applied from the preceding capacitor (e.g. 5C1). The chain circuits may be employed as "pattern registers", a combination of charges being set up on alternate stages in a chain. In the pattern register shown in Fig. 6, a pattern of positive charges may be set up on consecutive stages by selective operation of contacts 6S1a-d, one stage, e.g. the 4th, being left blank. Transfer pulses are applied to capacitors 6C1-4 on lines GP7-4 in reverse order as shown. Thus, charges originally set up on capacitors 6C1-3 would be shifted in the following manner: 6C3 to 6C4; 6C2 to 6C3; 6C1 to 6C2; then 6C4 to 6C1 and so on. If one input capacitor were initially charged negatively, this charge would be stepped in the opposite direction to a positive charge and at a faster rate. The stages in the pattern register may be grouped corresponding stages in different groups being connected to a common pulse supply line. In an unclosed chain circuit (Fig. 7, not shown), the capacitors are connected alternately to two pulse supply lines and a positive charge is stepped along to the end of the chain whereupon a negative charge, resulting from a mis-matched termination, is stepped back to the beginning and converted back into a positive charge, and so on; this circuit includes an input stage comprising a cold-cathode gas-filled triode. Fig. 8 shows an unclosed static chain circuit in which the diodes 8D1-5 remain triggered between the application of transfer voltages to lines 8P1, 8P2. The input capacitor 8C1 is initially charged through switch 8S1. When contact 8TR of a transfer relay (not shown) is subsequently operated, the +HT voltage is applied via line 8P1 to 8C1 thus triggering diode 8D1 which remains conducting through rectifier 8MR6 after capacitor 8C1 has been discharged and capacitor 8C2 has been charged through resistor 8R7. When the contact 8TR is released, the H.T. voltage is returned to 8P2 and applied to 8C2 whereupon diode 8D2 is triggered and capacitor 8C3 is charged, diode 8D1 being extinguished by the positive pulse applied to its cathode through rectifier 8MR17. Re-operation of contact 8TR causes a further transfer, and so on. This circuit also may be used as a pattern register, information being stored in alternate stages.