Patent GB-415783-A (GB)
Title: Improvements in or relating to electrical remote control systems
IPC: H02J13/00
Filed: 1933-03-03
Abstract: 415,783. Distant-control systems. STANDARD TELEPHONES & CABLES, Ltd., and ROCHE, A. H., Connaught House, Aldwych, London. March 3, 1933, No. 6464. [Class 40 (i).] In a distant-control system in which " on " and " off " movements of a unit are controlled by signals of different frequencies, a single tuned circuit only is provided at the receiving point, the circuit being automatically tuned from one of the signalling frequencies to the other after it has responded to a signal of the frequency to which it is tuned. As shown in Fig. 3, when a frequency of 480 cycles is received, a comparatively high voltage is generated across B, C of the inductance L and relay R1 operates, completing a circuit for R3. R3 locks across the mains A, B, connects in the load at its contact 4, opens the circuit of R1, closes that of R2, and removes condenser C2 from the tuned circuit, changing the resonant frequency of the tuned circuit to 1060 cycles. When the switching-off pulse of 1060 cycles is received, the voltage generated across C, B is sufficient to energize R2 which opens the circuit of R3, restoring the apparatus to its initial condition. In this embodiment the mains are assumed to be carrying direct current, but an embodiment of the invention using A.C. mains is shown in Fig. 4, the circuits in this Figure being so arranged that the tuning of the tuned circuit is not altered until the signalling pulse has terminated. When a pulse of 480 cycles is received, R1 energizes as in Fig. 3, completing a circuit through the right-hand winding of R3, which is shunted by a rectifier to enable the relay to hold on alternating current, a holding circuit for itself, and a circuit in parallel with contact 2 of R3 to hold C2 in the circuit. R3 pulls up completing the load circuit at its contact 4, opening the initial energizing circuit of R1, opening the normal circuit of C2 and closing its own locking circuit through its lefthand winding. The circuit remains in this condition until the signalling pulse terminates when R1 falls away, opening the circuit containing C2 to alter the tuning of the resonant circuit, and completing the circuit of R2. When the switching-off pulse of 1060 cycles is received R2 pulls up as in Fig. 3, opening the 'circuit of R3, which releases to open the load circuit, completing a locking circuit for itself and opening another point in the circuit containing C2 to prevent alteration in the tuning of the resonant circuit. When the pulse terminates R2 releases, restoring the apparatus to the condition shown in the Figure. In a further arrangement described, a single doublewound responsive relay R1 only is used, the relay locking mechanically until positively unlocked by the energization of its second winding by the releasing impulse. As described, three voice-frequency currents are available giving two selective operating conditions with a common release. The voice - frequency currents may be fed to the power circuit either directly or through transformers, may be fed by either the series or parallel methods, and, where branch mains are available, may be fed through a selector switch to any one of the branch mains to enable individual branch control to be effected.