An alarm system is provided in which an alarm condition causes a cellular transceiver automatically to transmit a telephone call to an alarm monitoring station by over-the-air transmission of a signal to a cellular site. A computer at the cellular site will cause communication between the cellular transceiver and an alarm company monitoring station. The alarm system includes a digital communicator with an alarm signal line connected to the digital communicator. The digital communicator is coupled to a cellular transceiver having a programmed keyboard, an audio input and an audio output. The digital communicator has an audio output and an interrogation input. The digital communicator's audio output is coupled to the cellular transceiver's audio input. The cellular transceiver's audio output is coupled to the digital communicator's interrogation input. The digital communicator includes a transmit enable output and a receive enable output. The cellular transceiver includes a transmit enable data line and a receive enable data line. The transmit enable output is coupled to the transmit enable data line and the receive enable output is coupled to the receive enable data line. An alarm signal received by the digital communicator causes the transmit enable output to transmit a signal to the transmit enable data line thereby enabling the cellular transceiver to transmit the telephone call via over-the-air transmission to the cellular site from where it is relayed to the alarm monitoring station.