Does the transmitter look like a big voltage regulator? If so, there are a couple of Mercury-cell batteries inside that power the transmitter. I remember those from back in the 50's and early 60's when Sun had the electric tach market pretty well sewed up. Good units, but those batteries had to be replaced pretty often!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!