Patent GB-781871-A (GB)
Title: Remote control system
IPC: H04L12/18
Filed: 1954-02-23
Abstract: 781,871. Electric selective signalling. WOLFINGER, J. Feb. 23, 1954, No. 5248/54. Class 40 (1). The individual elements of a collective indicator are controlled over the normal telephone network by predetermined signals including a frequency-selective pulse, whereby unauthorized operation of the indicator is prevented. Transmitter, Fig. 2. A telephone handset 1a establishes connection with the indicator location over a line selector 2 in the automatic exchange in the usual way, after which a thermionic oscillator 6 and a D.C. code impulse generator i1 are connected to line, in turn, to transmit a predetermined frequency pulse followed by a pulsed D.C. train characteristic of the transmitter, the line selector 2 being, in this case, arranged for through selection on a D.C. basis. Receiver, Fig. 2. When the indicator number is dialled a line relay A responds. The subsequent A.C. impulse is passed by a, filter F to actuate a relay Ws. Ws operates a start relay S, which locks and with relay A completes the circuit to a vertical and rotary selector 5 which is set by the D.C. impulses now sent from the transmitter impulser il pulsing the line relay A. Assuming that the indicator element 3a has been selected and that the lamp W1 thereof is alight, in which case relays V, W are energized, the wiper 7 of the selector 5 energizes a relay B, which de-energizes relays V, W, and locks as W releases. Relay W extinguishes the indicator lamp W1 and relay B lights B before the contact v1 of the delayed relay V has operated. A polarized relay P is also operated over wiper 7 and operates a relay K or L dependent on the position of contact v1 before V has relapsed. In the present case K operates. It locks over k1, de-energizes relay Sand over k2 connects a buzzer 11 to line for signalling back to the transmitter that the signal has been changed. When V relapses the signal element is ready to receive a new call. Relay K relapses after a predetermined time when its locking circuit is opened by a temperatureresponsive contactor T1. The next operation of indicator element 3a causes lamp W1 to be lit and B1 extinguished in a similar manner, relay L then performing the functions previously performed by K. Transmitter, Fig. 3. In this case after the indicator location has been dialled by the handset 1a, a frequency selective oscillator i3 is connected to line at i2 to transmit two A.C. pulses at the same time or different frequencies characteristic of the transmitter. Receiver, Fig. 3. The line relay A responds as before and then the relay Ws corresponding to the indicator element 3a associated with the operative transmitter is operated through a selective filter F1, by the first frequency selective pulse to energize a relay S which locks and operates a relay U so that the second frequency selective pulse passes through a selective filter F2 to operate a relay Ww. Each filter F1 is associated with a corresponding vertical busbar 9 and each filter F2 with a horizontal bus-bar 10 so that the operative filters F1, F2 effect a selection corresponding to that of a vertical and rotary selector. The selected relay Ww operates a relay Sb over the operated contact sw3 and de-energizes relay Sw to extinguish lamp w1 and light B1, relay Sb locking as Sw falls off. The delayed relay V is also energized by Ww and after its delay time releases S, U, when the unit is ready for a new change of indication. Signalling back is effected by relays K, L, P as in Fig. 2.