841,045. Television. FAIREY CO., Ltd. June 27, 1957 [March 27, 1956], No. 9603/56. Class 40(3). [Also in Group XXXVIII] A remote-control system for a vehicle, e.g. an aircraft, consists of a television camera in the vehicle for viewing the instrument panel or the external scene and a television receiver at the remote-control station for displaying the scene scanned by the camera, and signals are transmitted from the remote-control station to control the vehicle, the control signals being transmitted as successive series of pulses, the duration of each pulse representing the control signal magnitude for a corresponding control unit. A similar set of physical controls may be provided at the remote-control station to those actually in the vehicle, control members at the station generating control signals for corresponding control units in the vehicle. Two cameras may be provided one for the instrument panel and one for the external view. The latter may be actuated to scan views on either side and to the rear of the vehicle. Control signals. The control signal pulses are rectangular in shape and in each series of pulses the first pulse is a marker and frame-synchronizing pulse of relatively long duration and the leading edges of succeeding control pulses constitute line-synchronizing pulses. In the television signals transmitted white is represented by zero modulation, black about 70% modulation and the synchronizing pulses produce 100% modulation. Remote-control station equipment-control system. The control members control resistive transducers which produce variable D.C. voltages representing the control signals. These voltages 45, Fig. 5, are fed to gate circuits 46 which are connected in cascade and are. opened in turn in the order in which the control signals are to be transmitted. Each gate circuit consists of a multi-vibrator 47, a gate unit 48, a mixer 49 and a differentiating circuit 50. The control signal voltage can only be transmitted to the mixer when the gate is open. The first gate circuit is triggered by the pulse C produced from the marker pulse B by a differentiating circuit 54. Allthe multi-vibrators. receive the line-synchronizing pulses A generated by pulse generator 41 and each provides a pulse to open the corresponding gate 48 for the interval between a different pair of successive linesynchronizing pulses. The marker pulses B are derived at the correct intervals from generator 41 by a number of frequency dividing stages 42, 43 and a marker pulse generator 44. Transmitter. The common output 55 is supplied to a phantastron 56 which generates pulses of duration dependent on the magnitudes of the D.C. control signals. The marker pulse B is also supplied to the phantastron through a mixer 57 with a magnitude sufficient to generate an output pulse distinctly longer than any control signal pulse The rest of the transmitting circuit includes a pulse amplifier 58 and modulator 59 to control a. power amplifier 60 driven from a master oscillator 61 through a frequency multiplier 62. Receiver. The receiving equipment includes R.F. amplifier 71, frequency changer 72, I.F. amplifier 73, detector 74, video amplifier 75 and A.F.C. 77 and A.G.C. units 77, 78. Display equipment. The line-synchronizing pulses generated in the vehicle are separated in separator 81 and supplied to synchronize the time-base generator for two display tubes 83, 84 and also to control a video mixer 85. Electronic switch 86 is controlled by marker pulses B to cause alternate frames of the video output 87 to be supplied to each display tube. Alternate frames may represent the instrument panel display and the external view display in the vehicle respectively. Frame time-base generator 88 for the two tubes is also synchronized by the marker pulses B. A frame-blanking pulse generator also controlled by marker pulses B is provided to enable the operator to eliminate either display. Vehicle equipment-receiver and signal separating equipment. The vehicle equipment includes a receiver 101, Fig. 7, with A.F.C. and A.G.C. units 109, 110, a line-synchronization pulse separator 116 and a phantastron 118 for converting the received control signals from pulses varying in duration into D.C. pulses varying in amplitude. The phantastron generates a sawtooth wave which increases only for the duration of an applied pulse and then drops to zero. The D.C. pulses B<SP>1</SP> are supplied to a marker-pulse separator, limiter and differentiator 120 which is only responsive to inputs above a certain level. The outputs C<SP>1</SP> is fed to a coincidence-gate pulse generator 121 which generates rectangular pulses D<SP>1</SP> for opening the coincidence gate 122 whenever a marker pulse has arrived. The output 117 from the line-synchronizing pulse separator 116 is also applied to the coincidence gate so that only that pulse which passes during the coincidence-gate pulse will appear in the output E<SP>1</SP> from the coincidence gate. Control system in the vehicle. Output pulses E<SP>1</SP> are fed to the first of a series of D.C. output channels 125, one for each control unit in the vehicle. Each channel 125 includes a multivibrator gate-pulse generator 126, a gate 127 and a peak-level rectifier 128. The multivibrators 126 are connected in cascade and each gate is opened only during the interval between the reception of successive line-synchronizing pulses during which the control signal for that channel is received. The output B<SP>1</SP> from the phantastron is applied to all the gates and passes only when a gate is open to the corresponding peak-level rectifier 128 which produces an output proportional to the peak of the saw-tooth pulse applied to it. Vehicle camera equipment and transmitter. The two television cameras 131, 132 are controlled by the same line time-base and frame time-base units 133, 134. The outputs from the cameras are supplied through an electronic switch 137 to a video amplifier 138 and a video mixer 139. The electronic switch is controlled by the frame synchronizing pulses appearing in the output E<SP>1</SP> from the coincidence gate 122 to transmit the outputs from the cameras alternately. The outputs from the cameras may, however, be superimposed and either camera can be blacked out by the operator if desired. A line-synchronization generator 140 synchronized by the linesynchronizing pulses 117 superimposes linesynchronizing pulses on the video output in the mixer 139. These pulses control the synchronization of the line scanning of the display equipment at the remote-control station. The transmitter 150 includes a video amplifier 151 and a modulator 152 supplying a power amplifier 153 which is driven from a master oscillator 154 through a frequency multiplier 155. Aircraft "feel". In the case of an aircraft, mechanical "feel" is provided on the dummy controls at the remote-control station dependent on the magnitude of the air speed of the aircraft by transmitting from the aircraft a signal depending on the D.C. voltage derived from a Mach meter. This signal is represented by the duration of the line-synchronizing pulses generated in the aircraft using a phantastron. These pulses are separated in the pulse separator 81, Fig. 5, in the remote-control station and are then converted to signals for controlling electro-pneumatic relays controlling pneumatic dashpots associated with the dummy controls. Aircraft controls. Operation of the control column and rudder is effected by secondary closed-loop servo systems with position and velocity feedback while the remaining controls have position feedback only. Trimming of the ailerons, elevator and rudder are carried out by causing the remote-control station trimmer controls to adjust the average duration of the corresponding control signals. Other controls are two or three position controls or "on-off" controls. Several aircraft. A number of vehicles may be controlled at the same time by the transmission from the remote-control station of a combined signal composed of successive sets of control signals for each vehicle, while each vehicle transmits on a different carrier frequency. Safety precautions. If the equipment in the aircraft breaks down a holding relay disconnects all channel outputs so that the last command remains in operation or the aircraft may be made to revert to level flight or a separate command destruction link may be fitted so that the aircraft can be destroyed in an emergency. The relay will be disconnected automatically if the fault is in the receiver or if the aircraft gets beyond range of ground control. Duplicate transmission equipment may be switched in automatically in the aircraft if a fault develops in this part of the circuit. Instrument panel. The dial pointers alone may be white and the display unit at the remotecontrol station provided with copies of the dials with which the images of the pointers register. The transmission is then at 70% full power except when the white pointers are transmitted at zero power.