What is 7-level?
A small screwdriver with a fine tip and having a pen clip attached, making it capable of being easily carried in a shirt pocket.
This word originated with US Air Force electronics technicians and is derived from the skill level digit of the Air Force Specialty Code (AFSC) (example: 30670) where "7" indicates an advanced technician. The idea being that this small screwdriver is used to make precision adjustments to circuit board components such as trim potentiameters that require a higher level of technical skill to perform.
The 15 hertz circuit on the TACAN is a little off. Could I borrow your 7-level to adjust it?