Improvements in and relating to Servo Controls Between a Transmitter and a Receiver

1,180,940. Servo-systems. FRIED. KRUPP G.m.b.H. 25 May, 1967, No. 24334/67. Heading G4H. A servo control system between a transmitter and a receiver in which both the transmitter and receiver emit Gray code signals representative of their positions includes a logical circuit which compares the Gray codes to determine whether the number of ones from the highest track of the receiver to the highest track at which the codes do not correspond is even or odd to control the direction of movement of the servomotor. The invention utilizes the fact that if the number is even, the receiver is at a smaller angular position than the transmitter and vice versa. In one embodiment (Fig. 4) relay contacts a11-a61 (normally open) and a1-a6 (normally closed) are operated by the elements of the receiver Gray code, contacts b11-b61 and b1-b6 being similarly operated by the Gray code output of the transmitter. The contacts are cross connected so that if the number of ones is even current flow in channel A to the output a and if the number of ones is odd current flows in channel B to the output b. In another embodiment (Fig. 6, not shown) the switch contacts are replaced by transistors.