This is what happens when a burglar alarm panel communicates with the police or a monitoring company using the 'Contact ID' format; (my cell phone, in this case)

I used my computer to generate the handshake and ACK tones, the first sound heard is my cell phone ringing.

First the alarm panel dials the number and the monitoring company (receiver) picks up and plays back a handshake which is 100milliseconds of 1400hz followed by 100ms of silence then 100ms of 2300hz.

Then the alarm panel sends a bunch of DTMF tones indicating the situation, then the receiver plays back ~750ms of 1400hz as an acknowledgment, then more tones follow, another ack, repeating until all messages are sent and a final ack then it hangs up.

For most alarm situations, the total time spent on the phone is less than 30 seconds.

The Contact ID standard;
www.smartelectron.ru/files/DC-05_Contact_ID.pdf