Traditional Analog CID Monitoring

When alarm systems first started reporting to a central monitoring station they often used a third party alarm dialer. This device had one or more inputs onboard, which would initiate a phone call to a central monitoring station. The dialer would use either a series of pulses or beeps, or DTMF tones to communicate a message to an alarm receiver at the monitoring station, much like morse code.

As alarm monitoring became more popular, more and more alarm panels came out with onboard dialers, and the industry started to settle on a number of standards or protocols for the communication of alarms.