Before airplanes go off into the wild blue yonder, attention must be paid to their avionics. Tel-Instrument Electronics manufactures avionics test equipment for the US Army, the US Navy, and other military and commercial customers. Tel's instruments are used to test navigation and communications equipment installed in aircraft, both on the flight line (known as ramp testers) and in the maintenance shop (bench testers). The US government and military avionics customers (such as Boeing) account for more than two-thirds of sales.