Patent GB-1304104-A (GB)
IPC: H04N5/44
Filed: 1970-04-29
Abstract: 1304104 Receiver tuning arrangements PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 29 April 1970 [2 May 1969] 20670/70 Heading G4H [Also in Division H3] A tuning arrangement for a receiver has signalling devices 24 controlling bi-stable trigger circuits 11 and an electric locking arrangement 15 is coupled to all the bi-stable circuits so that when one bi-stable circuit changes from its first condition to its second condition the electric locking arrangement 15 brings any other bi-stable circuit previously in its second condition to its first condition. An electronic switch 28 is closed when an associated bi-stable circuit is in its second condition so as to connect an associated variable resistance voltage divider 29 across a stabilized voltage supply 37 -40 and to apply a tuning voltage to electronically controllable reactances 5a, 5b, 5c. The variable division point of one of the dividers is mechanically coupled to a tuning dial 10 and a tuning knob 9 and the associated bi-stable circuit is brought into its operative state when the tuning arrangement is rendered operative. As shown each bi-stable circuit 6, 7, 8 includes a gas discharge tube 11 which are coupled to a common cathode resistor 15. When tube 11 in circuit 6 is triggered by touching contacts 23, 25 of the signalling device 24 with a finger tip the voltage change across the cathode resistor 15 causes the voltage across the previously on tube, say in circuit 7, to fall so that this tube becomes extinguished. The tube 11 in circuit 6 is now on and causes transistor 28 to bottom and connect a voltage from the tapping on potentiometer 29 via an isolating diode 32 to variable capacity diodes 5a, 5b, 5c in the tuner 1 which includes R.F., mixer and oscillator stages. The voltage change at the resistor 15 also triggers a monostable circuit 44 which acts via line 45 to cut-off the A.F. stage 3 during the changeover of tuning. The tuning unit selected 6, 7 or 8 is indicated by the gas discharge tube 11 which is energized or by a lamp associated with the selected unit. The tuning voltage is stabilized by Zener diodes 37, 38 and the trigger electrode of the tube in unit 8 is connected to an A.C. supply via a resistor 35 and capacitor 36 so that unit 8 always becomes operative when the receiver is first switched on. Unit 8 provides manual tuning via knob 9 which is coupled to an associated potentiometer 29 and to a dial 10. The ends of the tuning range are adjustable by the potentiometers 40, 41. Primary electrodes 26 maintain preionization and facilitates ignition and resistors 42, 43 provide linear tuning. The transistor 28 may be controlled from the cathode line and the resistor 15 may be made common to the anodes of the tubes. For use in battery operated receivers the bi-stable circuits may be cross coupled transistors, or may be silicon controlled switch and the signalling devices 24 are then push button contacts. Alternatively to retain fingertip operation the device 24 is connected to the base of a common emitter bipolar transistor. The isolating diodes 32 may be replaced by a single diode (47, Fig. 2, not shown), common to all the units 6, 7, 8 and these diodes 32, (47) also act to compensate the tuning diodes 5 for temperature changes. In a modification (Fig. 3, not shown), a wave range switch (48) of the tuner 1 is provided for medium and long wave reception and is coupled to a switch (49) selecting alternative potentiometers (29m or 29l) at the collector of transistor 28. Switch diodes may be used for range switching of the tuner 1 and the units 6, 7, 8 may have a preselector switch to provide the switch voltage for the tuner 1 via transistor 28 or through electronic switches controlled by the bi-stable trigger circuits 11. The tuning may be effected by remote control by transmitting by radio signals from the signalling devices to the bi-stable circuits.