A burglar alarm control panel reports to a monitoring center that smokes have been reset| Played 21 times
Recently someone uploaded a recording of an alarm monitoring center device playing tones on a phone call. Years ago I recorded the alarm panel we used to have reporting that the smoke detectors had been successfully reset after a fire incident (IIRC a cooking-related setting off of a smoke detector). You hear the alarm panel dialing (some digits of the phone number bleeped out), two rings, then the monitoring center answers. It tries a few protocols before finally trying one the panel understands. The panel then sends its report (the lower tones you hear are the panel), at which point the monitoring center sends back a tiny confirmation message and waits for another signal. The panel, its report complete, hangs up instead.