GB732320A - Improvements in and relating to remote control systems - Google Patents

Abstract

732,320. Electric control systems. GENERAL ELECTRIC CO. Aug. 4, 1953 [Aug. 1, 1952], No. 21486/53. Class 40 (1). Three control functions are effected by transmitting respectively electric oscillations (a) at a frequency f1, (b) at a frequency f2 and (c) at a frequency recurrently varying from f1 to f2 at a recurrence frequency less than f1 or f2. At the receiver, the control frequency f1 may be used, e.g. to cause a prime mover to deliver more power, f2 to reduce the power of the prime mover, and the varying control signal to preclude actuation of either of the other two controls. Transmitter. In the lower position of a single pole-control switch 18 a relay 8 is held energized to short circuit, as shown, the input terminals 2, 3 of a transmitter 1 which is thereby caused to generate oscillations at a frequency f2. In the upper position of the switch the relay 8 is held de-energized by a low resistance 21 connected in parallel therewith. The input terminals 2, 3 of transmitter 1 are thereby open circuited causing oscillations at frequency f1 to be generated thereby. With the switch 18 in its central position the relay 8 self-interrupts, at a frequency determined by a capacitor 16, periodically to short and open circuit the input terminals 1, 2 whereby the transmitter frequency varies in step between f1 and f2. The output of transmitter 1 is transmitted over a carrier current channel la or by radio. Receiver. A discriminator 22, e.g. as disclosed in Specification 648,278, [Group XL (c)], develops any output of positive polarity across series connected load resistors 24, 25 when frequency f1 is received, a negative output when frequency f2 is received, and an alternating output at the " recurrence " frequency where a frequency modulated wave varying between the frequencies f1, f2 is received. When a control signal at frequency f1 is received, the positive signal potential at point 58 causes the associated tetrode 28 to conduct, energize a relay 48 to effect the desired control over contacts 51, 52 and at the same time preclude tetrode 33 from operating. When a control signal at frequency f2 is received tetrode 33 conducts, effects the desired control over relay 53 and contacts 52, 56, and effectively blocks tetrode 28. When the control signal received recurrently varies between f1 and f2, the alternating output at 57-58 is rectified at 41, 44, such that the rectified voltages appearing across capacitors 42, 45 reduce the potentials of the grids positively to block both tetrodes 28, 33 and so preclude operation of either relay 26 or 27.