Torben: Thanks for the initial feedback. The other device is sometimes another flash, sometimes a counter, or could be tied to a relay, but it doesn't matter, as every other device I try is being set off by the faster initial pulses.
I don't want a photodiode to detect the first flash, I am trying to sync the two events via hardwire. I have used the 555 chips before in some simple timing circuits, and don't know just how that might be used to detect when the pulse goes to a longer duration. Can you describe it in more detail for me?
Simpler is definately better, and I would also like to try and find a way without using the 555, if that is at all possible.
Again, thanks all in advance to all for your input and possible suggestions!
Michael