- noun a device which gives off a sound or light as a warning or to indicate if something is active
- noun a device which gives off a sound or light to indicate which of several electrical circuits is active
- noun a signal which can be heard or seen in order to attract attention
- An electrical signaling device that identifies when a circuit is engaged.
- An electrical device which utilizes sounds and/or lights to signal an event or circumstance. For example, a blinking light indicating an incoming call.