Traditionally, a small physical lamp (or a pair of red and green lamps) mounted underneath a monitor or on a camera which indicates whether the source routed to the monitor or the camera is “on air”; may also be part of a UMD or OMD. In analogy, nowadays also used for a small indicator underneath a PIP on a multiviewer head. Conventionally, a red light means “on air”, green means “in preview” (i.e., is the next signal that will be switched to air), and yellow means “recording”, but can be used to convey any arbitrary status (for example “device is currently being operated remotely, do not touch”).