Explanation: A synchro transmitter and receiver system is an electromechanical device specifically designed to accurately transfer angular position from one location to another. The transmitter unit is mechanically linked to a rotating component, such as a directional antenna's mast, converting its angular position into an electrical signal. This signal is then sent to the receiver unit, which precisely mirrors that angular position, typically driving an indicator dial on a control unit. Therefore, option C is correct because synchros are essential for providing real-time feedback on the direction a rotatable antenna is pointing. Option A is incorrect as synchros do not synchronize pulse trains; that's related to timing in digital or radar systems. Option B describes the function of a transmit-receive (TR) switch in pulsed systems, which protects the receiver during transmission. Option D refers to motor speed regulation, which is not the primary purpose of a synchro system, although the receiver does act like a motor to follow position.