To elaborate: It's a requirement that amateur radio stations periodically identify themselves by the operator callsign during transmission. For unmanned station

To elaborate: It's a requirement that amateur radio stations periodically identify themselves by the operator callsign during transmission. For unmanned stations like repeaters this is usually accomplished with an automatic morse-code transmission of its callsign. The transmission occurs if the repeater has been activated, usually every 10 mins or so after a moment of silence, or after a longer period of silence, whichever comes first. (The repeater users still have to identify themselves with their own callsign during use of a repeater.)