[tongue-tied]

No more ATR/ATN, but now they have ATO and ATI for O and I level. It sure does make an advancement exam more realistic when you turn wrenches and screwdivers but don't have to answer questions like "What will the voltage drop at C1 be if R33 fails?"

Never knew of ATR/ATN. I heard of ADR for recip and ADT for turbojet, but can't remember different tweets.

[NY Attitude]

ATR = Radar Technician and ATN was for communication equipment. ADR as you said was for recips and ADJ was for jets. As for the question, are we discussing a regenerative feedback circuit? Since the company I work for provides equipment to the US and other Navies, the highest maintenance level for the US Navy is O level both for aircraft and for shipboard equipment.