I have not quite been able to figure out what it is that I would need specifically, to switch on a circuit ( with High Voltage) using an IR LED, or even a normal LED when its path is blocked ( low to no light ) to a sensor. And I quite honestly am not sure what type of sensor I should really look for. A photo-diode, or possibly a photo-transistor? It seems that the diodes that can handle upwards of 300vdc are far out of the price range for me, So i was thinking perhaps a photo-transistor would work better, although most of these things are trigger on light, instead of triggering on no light ( IR light is block, or maybe even use a small laser and laser sensor? ). The ability of the circuit to switch on extremely fast is important, and I need it to be built in a certain fashion that allows the use of the HV circuit becoming complete. Basically, the light path will be blocked, and in short order I need a HV circuit to activate in response. Voltages up to around 1kv will be used in the activated circuit, the path 'trip switch' does not need to be powered on the same circuit if that makes things easier.