and a servomotor. Control type synchros are used in applications that require large torques or high accuracy such as follow-up links and error detectors in servo, automatic control systems (such as an autopilot system). In simpler terms, a control synchro system is a system in which the transmitted signal controls a source of power which does the usable work. Quite often, one system will perform both torque and control functions. Individual units are designed for use in either torque or control systems. Some torque units can be used as control units, but control units cannot replace torque units. Synchro functional categories A synchro will fall into one of eight functional categories: Torque transmitter (TX) Input: rotor positioned mechanically or manually by the information to be transmitted. Output: electrical output from stator identifying the rotor position supplied to a torque receiver, torque differential transmitter or a torque differential receiver. Control transmitter (CX) Input: same as TX. Output: electrical output same as TX but supplied to a control transformer or control differential transmitter. Torque differential transmitter (TDX) Input: TX output applied to stator; rotor positioned according to amount data from TX that must be modified. Output: electrical output from rotor (representing an angle equal to the algebraic sum or difference of rotor position angle and angular data from TX) supplied to torque receivers, another TDX, or a torque differential receiver. Control differential transmitter (CDX) Input: same as TDX but data supplied by CX. Output: same as TDX but supplied to only a control transformer or another CDX. Torque receiver (TR) Input: Electrical angle position data from TX or TDX supplied to stator. Output: Rotor assumes position determined by electrical input supplied. Torque Differential Receiver (TDR) Input: electrical data supplied from two TX's, two TDX's or from one TX and one TDX (one connected to the rotor and one connected to the stator). Output: rotor assumes position equal to the algebraic sum or difference of two angular inputs. Control transformer (CT) Input: electrical data from CX or CDX applied to stator. Rotor positioned mechanically or manually. Output: electrical output from rotor (proportional to sine of the difference between rotor angular position and electrical input angle. Torque receiver-transmitter (TRX) designed as a torque receiver, but may be used as either a transmitter or receiver. Input: depending on the application, same as TX. Output: depending on the application, same as TX or TR. Operation On