Elpro Repeater Self-Watchdog
(mains powered version)

It must be remembered that electronics is involved with radio telemetry systems and inadvertent "lock-ups" can occur but can become a major issue especially if all that is required is a power-down power-up cycle (total failures cannot be remotely repaired).

With some careful programming and the circuit below a power re-cycle will occur on comms failure.

A full explanation of the workings of this circuit are given on this page and can be referred to if required.

The capacitor is 4700 F (min) @ 25V
The resistor is 100 ohm -watt
The sense relay is a miniture SPDT 12Vcoil e.g. LZ12 (coil > 390 ohms)
The power relay is a miniture DPDT 12Vcoil e.g. RZ12/2 (coil > 390 ohms)
The battery is the typical 12V 10A/h back-up battery and only fitted if required.

If there are any questions please email


09.07.00