capacitor voltage 20 volts in this embodiment has been reached and also a maximum ignition delay period of time has elapsed after the power supply is activated after half a second in this embodiment the micro controller then switches the primary coil off after a preset period of time the load interval in this embodiment about 100 msecs if the minimum voltage has not been reached the primary coil will not be switched on the micro controller is further programmed to fully discharge the capacitor after current from the power supply is removed in this embodiment by switching the primary coil on again to prevent the secondary coil from remaining on from current remaining in the capacitor voltage drop loss in the wiring between the power supply 31 and the latching device 9 is no longer a significant problem with the method and design of the present invention a smaller gauge wire may be used for the wiring between the power supply 16 as well eliminating the need for special retrofitting of the electrical system of a building fig4 is a circuit diagram of a preferred embodiment of the circuit of the invention to be used with generally available latching devices fig4 is a preferred embodiment of the circuit of the present invention and designed to work with von duprin types of electric latch retractors such models el 33 and el 99 a 24 vdc power supply 31 supplies current to a high current relay switch 33 the switch 33 may be mechanical or an electronic equivalent such as an electronic switch implemented with.