Patent GB-1121774-A (GB)
Title: Selective switching circuit arrangement
IPC: H03K17/64
Filed: 1967-03-02
Abstract: 1,121,774. Controlled non-linear inductors; television; transistor delayed pulse generators. AMP. Inc. 2 March, 1967 [24 March, 1966; 30 Aug., 1966], No. 9854/67. Headings H3B, H3T and H4F. In a switching circuit in which a selected one of a plurality of signal inputs is connectable through relay contacts to a common signal output and causes the delayed disconnection of the input previously connected, operation of the relays is determined by transfluxors each associated with a different input. First embodiment, Fig. 3. Signal inputs a, b, c, d are connectable through switch modules 48 to a common signal output 10, control of the relays RC1, RC2 in each module being effected through a respective transfluxor 31-34 each comprising a major aperture 35 and four minor apertures 36-39. When a control push-button 21- 24 is depressed one transfluxor, e.g. 31, is set and the remainder are cleared, a transfluxor in the set state enabling a drive signal from an R.F. source 46 to be coupled through its output winding 51-54 to an associated gate and delay circuit 47. Within this circuit a transistor Q1 becomes conductive and relay operating current passes through a smoothing circuit R2, C2, R3, C3, C4. The two relays RC1, RC2 operate immediately and condenser C5 charges up slowly through a high resistor R4. In the previously operated circuit, the transfluxor (e.g. 34) now in the cleared state ceases to transmit an output to its gate and delay circuit. Consequently the transistor Q1 is cut off, and the operated relays RC1, RC2 are released after a delay determined by the discharge of condenser C5 through a diode D1 and the relay windings. Second embodiment, Fig. 5. Three - aperture transfluxors 71- 78 are used in association with push-buttons 61-68 and a driver 60 of which terminal t2 is initially of low impedance, terminal t3 of high impedance, while a third terminal receives synchronizing signals such as the frame pulses of a television system. When a push-button is operated, the associated transfluxor is set by winding 79 and current passes directly to low impedance terminal t2. After a delay determined by the driver 60 and when a synchronizing pulse is received, the impedance conditions of terminals t2, t3 are reversed so that current passes through the clear windings 84 of all the cores. The previously operated relays are then released. Driver, Fig. 6. A single push-button 61, the set winding Ns of the associated trans-. fluxor and the clear windings Nc of all the transfluxors are shown. When the push-button is closed, capacitor C12 commences to charge through resistors R11, R13, .R14. Synchronizing (frame) pulses are applied to terminal 85, each pulse causing a transistor to conduct and so draw current through R16, R17, R18. from the B1 electrode of a unijunction transistor Q13. When the charge on C12 nears the conductive voltage of Q13, the next synchronizing pulse causes a voltage change at B1 so that the condenser discharges through Q13 and R20 to ground. Junction P3 becomes positive and fires a thyristor Q19, so completing a discharge path for a previously charged condenser C11 through a diode D11, a pulse forming inductor L1, push-button 61, the set winding Ns and the thyristor. This pulse, sets the associated transfluxor. At the same time the positive pulse occurring-at P3 is coupled through a D.C. blocking condenser C15 to the base of a transistor Q15, this transistor together with transistor Q16 forming a monostable multivibrator. Transistor Q15 ceases to conduct and Q16 becomes operative. Capacitor C18 is now connected to charge at a rate determined by an R.C. network including C18, R30 and R1, this network determining the time during which two transfluxors are both operative. When the potential at junction P4 in the charging circuit becomes sufficiently negative, Q15 will conduct to cut off Q16 and the junction P5 will swing positive. This fires thyristor Q9 by a pulse through C14. By this time capacitor C11 is recharged, and when the thyristor fires produces a pulse which passes through windings Ns and Nc, thereby clearing the previously operated transfluxor.