Today I pieced together this capacitive discharge firing box:
It charges a 130 uF capacitor to 340 V, storing 7.5 J
A significant fraction of the 7 odd Joules is wasted in the flash lamp used as a thryatron, but most of it makes it to the e-match. A short stainless steel turning from a pot scourer explodes into a shower of sparks at the end of a metre of cat-5 cable.
The continuity test is implemented with a Neon bulb, which also acts as the charge indicator. The test loop current is 150 uA. The only disadvantage of this is that several hundred kR is sufficient to light it, even your fingers across the output will work nicely. In practice, even with a hundred metres of shooting wire the insulation leakage is far below lighting the neon. One issue with the way I have wired it is that there must be something across the output to light the Neon, open it looks just like it is discharged, so you must put a shorting link across it when it is not wired up to the shooting circuit - that's a bit of a safety issue, but there just wasn't any more room inside the box for a more complex circuit.
With the unit I can easily fire this composition through several metres of wire;
12 Potassium Nitrate
1 Lampblack (conductive)
1 Charcoal (airfloat)
It results in an e-match that measures 45 Ohms or more and will basically not fire with a conventional system. (Don't use this composition it was only a test to see how insensitive the e-matches could be and still relibably ignite. I passed an Amp or two DC through it and managed to roast the sulfur out of it as a yellow vapour, but not ignite it. The CD unit exploded it with a sharp crack. It does make a good pyrogen for bridged matches though). My other bridgeless e-match compostion works just fine, as do bridged matches. With a bridge wire of 34# or finer you can use over 100 metres of wire (the longest I've tried - probably *much* longer).