Patent GB-662668-A (GB)
Title: Improvements in electrical systems of remote control
IPC: H04Q9/00
Filed: 1949-04-26
Abstract: 662,668. Electro selective signalling. GENERAL ELECTRIC CO., Ltd., and WORDEN, W. R. March 1, 1950. [April 26, 1949] No. 10995/49. Class 40 (i). In an electric signalling system wherein both selection and control functions are effected over the same pair of line wires at different times, a change in selection is initiated by means of a disconnection on one line wire to release the selection condition previously set up, followed by application of potential to the one or both line wires to effect the desired selection, the selecting operating being terminated by a momentary break on the second line wire whereupon normal control functions are reestablished. Selection is effected by a multipoint control'switch adapted to apply current of either polarity to one or both of the line wires to energise a combination of line relays at the controlled point corresponding to the control switch position ; the line relays effect operation of the appropriate selecting relay after which the line relays operative over the second line are usable for control functions and both wires are usable for speech transmission. The system may be used for the selection of electrical meters, switches, speech channels, etc., but is described as applied to the control of a multi-frequency transmitter associated with a multi-frequency receiver, or alternatively, with a number of receivers pre-tuned to fixed frequencies, and to the selection of the operating frequency. Fig. 1 shows the control station where a six point switch SC having two banks SC1, SC2 selectively controls the operation of six selector relays E, F, G, H, J, K, at the controlled station Fig. 2, which determine the operating frequency of the transmitter and receiver(s) located thereat. Assuming the selector switch to be set, as shown, in its first position, for frequency F1, switching on the power supplies at switch ON energises slow-torelease relay AC. Relay AB operated thereby, locks and de-energises AC and when after its delay period, AC releases, a relay AK, Fig. 1, is operated in series with the line relay C at the controlled station, Fig. 2, over selector switch wiper SC2 and line 1. The operated line relay C applies power to the filaments of the transmitter and receivers at C1 and energises relays E, Z in series, these relays locking at E1. The selector relay E energises at E2 relays causing the transmitter and receiver to operate on frequency F1. Relay Z operates a slow-torelease relay Y whose sole function is to maintain the filament currents during subsequent operation of the various line relays. Relay Z also operates a relay CO which locks and at CO3 short circuits a paralysing bias normally applied to all the receivers, to bring the receiver responsive to frequency F1 into operation and connect its output to line over transformer TR5. At the control station relay AK releases AB, lights the "listen" lamp and energises a slow-to-operate relay AQ. Relay AC operates as AB falls off, and the receiver output as fed from AL, the line L1, L2 over transformer TR1 to the operator's loudspeaker or headphones. If the operator wishes to speak, the "speak listen" switch on his telephone is thrown. This operates a relay AT which extinguishes the "listen" lamp, connects a microphone and amplifier to line at AT2 in lieu of the loudspeaker, and over AT3 and line L2 energises relays AL, A. Relay AL lights the "speak" lamp and relay A Fig. 2, removes at A3 the paralysing bias from the transmitter and applies it to the operative receiver. Relay A also operates a relay DA to feed the high tension supply to the transmitter. The operator may now speak over the line and transmitter and may restore the apparatus to "receive" conditions at will by releasing his "speechlisten" switch which releases relays AT, AL, A, DA. This "speech-listen" change over may be effected as often as desired. To operate the transmitter under telegraph conditions a switch S2 is closed to energise a relay AM which changes over the operator's line connections for telegraphy transmission, and over contact AM3 and line L2 energises relays AL and line relay B. Line relay B operates relay M which changes over the transmitter and receiver conditions from speech to telegraph, applies HT to the transmitter and renders the transmitter operative and receivers in-operative by suitably switching the paralysing bias at M3. The telegraph lamp is lighted by relay AL and the operator may now operate his key to transmit over the line wires to the transmitter. Restoration of switch S2 releases relays AM, AL, B, M permitting the reply to be heard via the operative receiver. To effect a change in the operative transmission and reception frequency the selector SC is moved to the setting desired, e.g. position 4 corresponding to frequency F4. As soon as wiper SC2 moves relay AK and line relay C release. Line relay C releases relays Z, E, CO, to cancel the previous frequency selection while at the control station AK releases AG, extinguishes the listen lamp and operates relay AB which locks. Relay AC de-energised by AB releases after an appreciable interval. As AQ falls off line relay A is energised over selector switch wiper SC1 and line L2, and when AC releases, relays AK, D operate in series over line L1 and wiper SC2. As both line relays A, D are now operated, relay Z operates in series with selector relay H and they lock at H1. At H2 relays are operated to render frequency F4 operative in the transmitter and receivers, while at the control station, AK releases AB and operates AQ slowly which when it finally pulls up releases line relay A. Relays AC, CO reoperate whereupon the line wires are once again ready to be used for control purposes as above described. Frequency selection by the selector wipers SC1, SC2 is thus effected by energising the line relays in combination over line Ll or both lines L1, L2 subsequent control functions being effected over line L2 only by line relays A, B. Line Ll remains energised during such control functions to hold the operative selector relay C or D.