A device for redirecting alarm-messaging from an alarm control panel from its connection to the PSTN to a backup radio transceiver for transmission of the alarm signaling to a central alarm station via a radio network. The switch-over to the radio network occurs not only when the PSTN line is down, for whatever reason, but also occurs when the PSTN line is already occupied by an existing transmission by a premises' telephones, in order to allow the user to make a call over the PSTN during such an alarm condition. Moreover, if during the time the alarm control panel is transmitting its alarm messages over the PSTN, a premises' telephone goes off-hook, the device of the invention terminates the alarm panel's connection to the PSTN and automatically switches over the alarm panel to the radio backup system.
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