Selsyn

Part of speech: noun

Definitions

1. An electrical device that keeps a remote shaft turning in step with another, reporting its angular position through wiring
2. A synchro-type motor or generator used to send the rotational position of one shaft to a distant receiving unit
3. An electromechanical transmitter and receiver pair that matches the angle of a remote shaft to a control element

Etymology: Selsyn is a clipped form of "self-synchronizing," a name that describes what the device does: it keeps a remote motor or indicator in step with a transmitter without any external timing signal. The word is therefore a compound built from "self," meaning acting on its own, and "synchronizing," from the Greek roots "syn" (together) and "chronos" (time), so the whole name says the device keeps time with another device by itself. The shortening is the notable part. Long technical names often get trimmed in workshops and engineering shops until a single short form replaces them, and "selsyn" followed that path, becoming the everyday term for the component. The result is a word whose full form is rarely heard, which explains why many people meeting it for the first time have no idea it is a contraction at all.

Synonyms: synchro, synchronous motor