ARRL, American Radio Relay League and RSGB, Radio Society of Great Britain have published handbooks over the years that are made for amateur radio. The oldest edition of the ARRL Handbook that I have in the office here is 1994 and much of it still deals with vacuum tubes. I'd suggest looking for mid-90s and older amateur radio publications.
thanks for your help!
Does any one now how an electrosurgery unit really works, i mean how much is the voltage output and the current that flows through the patients body!!??? :?: