Patent GB-425626-A (GB)
Title: A device for automatic and remote control of tuning apparatus in radio receiving sets
IPC: H03J7/30
Filed: 1933-09-30
Abstract: 425,626. Wireless receiving systems. BROWN, L. H., 187, South Lambeth Road, London. Sept. 30, 1933, No. 26961. [Class 40 (v)] [See also Group XXXVIII] An automatic tuning system for wireless receivers, including television receivers, comprises a motor to drive the tuning controls and automatic means to stop or disconnect the motor on reception of a carrier exceeding a predetermined strength. The receiver may be switched on from a distant point and may be distantly controlled to reject any undesired selected carrier, while after an unsuccessful search for a carrier, the receiver is automatically switched off. In the drawings, pairs of terminals such as 23 represent sources of voltage for operating relays. The receiver 11 is switched on by push 115 which operates relay 100 to complete the voltage supply circuit 103. The radio or intermediate frequency output of the receiver is tapped off by lead 10 and applied, preferably over a band-pass filter 12 tuned synchronously with the receiver, to the grid circuit of valve 15 over a rectifier 13. Alternatively, the grid of valve 15 may be biassed by the automatic gain control of the receiver. Anode current of 15, in the absence of a carrier of predetermined strength operates relay 18, the anode current being suitably adjusted by resistance 19. Relay 22 operates, energizes relay 30 and completes the heater circuit of a thermal delay switch TDS, which after say 30 seconds, operates one or other of solenoids 33, 34, depending on the position in which a swinging contact 84 was last left by relays 41, 51. Assuming 33 operates, armature lever 60 moves clockwise and carries bevel wheel 72 into engagement with the motor driven bevel 68, the motor 66 having been switched on at contacts 63 of the armature. Alternatively a clockwork or other motor may be used. Bevels 72 and 71 for opposite directions of rotation are carried by a sleeve 69 which is now clutched at 73, 74 to shaft 70 which drives the tuning apparatus. When a carrier above the predetermined minimum strength is found, valve 15 is biassed over rectifier 13 so that relay 18 falls back followed by 22 so that solenoid 33 de-energizes, disconnects the drive and stops the motor. The tuning control is assumed to turn forwards and backwards through 180‹, and if the shaft 70 rotates to the end of its travel in one direction without a carrier being found, cam 76 thereon closes contacts 80 to operate relay 51 which reverses the swinging contact 84 so that solenoid 34 operates in place of 33 and reverses the drive. Contacts 79 also operated by cam 76 energize relay 130 which locks up. When the shaft has been driven in the reverse direction through 180‹ without a carrier being found, cam 76 operates contacts 81 to energize relay 120 so that relay 100 receives an impulse to switch the receiver off. Relay 100 is of the type which closes its contacts on receipt of an impulse and opens them on receipt of a second impulse. There may be more than one control point, the control switches being wired in parallel. Rejection of a selected setting. Switch 90 or 91 is closed according to whether it is desired to select a higher or a lower wave length. Relay 41 or 51 pulls up, energizes one or other of the solenoids 43, 44 to drive the motor and operates relay 92 which shortcircuits the thermal delay switch which is not required for manual control. The operated relay 41 or 51 remains held for the present over contacts of relay 30 which is not operated at this time since the receiver is tuned on a carrier; switch 90 or 91 may therefore be released. When the receiver has gone off tune, 21, 22 and 30 pull up and relay 41 (or 51) falls back and the receiver is tuned afresh as previously described. Switching off. If both switches 90, 91 are operated simultaneously both relays 41, 51 pull up and relay 100 receives an impulse to switch off the receiver. If it is desired to switch off when a transmitting station which is being received shuts down, switch 112 is operated to energize relay 110 which locks up and prepares a circuit for relay 100, the switch being released. When the carrier ceases, relays 20, 22 pull up and the receiver starts to retune, but relay 92 on pulling up completes the circuit of 100 which switches off the receiver.