All,
One more thing – The older units used six AA batteries instead of four CR123A batteries. AA batteries are 1.5v so 6 x 1.5 = 9v. If you use the diagram above you will need to reduce the voltage accordingly. I am sure old heads will just go digging around in their supplies, but if you want a commercial off the shelf (COTS) solution, this $9 device will get it done for you.
73
Phillip