To assure seiqure when required, the line is wired in series through the RJ31X. From there, tip and ring pass into the alarm equipment where a relay decides wheter the dial tone will go back out to the other jacks (on T1 and R1), or seized for use by the alarm.
Any network interface jack that can allow a connected device to disrupt basic telephone service to other devices because of its wiring configuration (for example, by running tip and ring through a relay) must have a provision to automatically return service to the other locations if the seized device (the alarm unit) malfunctions.
This is accomplished with shorting bars. Gold plated metal tabs inside the RJ31X device will provide direct connection of tip and ringback to the other locations (bypassing the alarm device) when the miniature 8 postion plug is remove from the jack. Inserting the plug lifts the gold plated contact wires away from the shorting bars. and extends the tip and ring circuit to the series leads going into the alarm device.
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