Consider also the electronic deployment altimeters. The instant you arm
> them, they are sending low level current through the flashbulb or ematch.
> It's enough to check continuity, but not enough to fire the charge. I've
> NEVER heard any one suggest that the altimeter continuity checks be removed
> for safety reasons.
What I like to do with altimeters is use a 3-position arming switch in the pyro power circuit: in addition to "off" and "on" there's a "test" position - this connects a 150 ohm resistor with a high brightness LED in series with the firing current path... the idea is that an altimeter failure that would cause a premature firing (such as a shorted output transistor) will be detected before it causes trouble, but the altimeter can still complete its continuity check.
(The switches I use are miniature C+K rotary switches... I figure these are less likely than toggle or slide switches to be shifted out of position by G forces.)
-dave w