As a circuit element, the synchro is essentially a variable-coupling transformer; the magnitude of the magnetic coupling between the primary and secondary, and hence the magnitude of the output voltage, varies according to the position of the rotatable element. In function, the synchro is an electromechanical transducer. A mechanical input such as a shaft rotation is converted to a unique set of output voltages, or a set of input voltages is used to turn a synchro rotor to a desired position.
Synchros can be classified in two overlapping groups: torque synchros and control synchros.
Torque synchros include transmitters (CG), differentials (CD) and receivers (CR).
Control synchros include transmitters (CG), differentials (CD) control transformers (CT), resolvers (CS), linear transformers (LT) and the two hybrid units: transolvers (CSD) and differential resolvers (CDS).