Abstract: An alarm system, including ease of programming of a family or group of interoperating alarm devices via a learn mode that detects new devices and provides reliable accounting of the group via state dumps to an external system. Reliable communications with the external system are provided via a set of protocols. Disabling of the alarm system is prevented, by transmitting a pre-alarm signal prior to expiration of an entry delay, and by verifying communications with an external device, prior to an alarm-triggering event. Multi-priority message code assignment, including error tolerance, employs n-bit codes with maximized error tolerance. Message transmissions include multiple levels of error protection. The group of monitored alarm devices can be easily set up, purchased and activated by a consumer, and do not become permanent fixtures.