The Gulfstream G-280 Fuel Quantity test box speeds diagnosing failed Capacitance Probes, and wire harness failures.
Each of the LOW-Z selection test switches connects the Barfield LOW-Z to the specific probe.
The switch is labeled with the AMM Nomenclature for the probe, (10Q OUTER RT #1), as well as the IPC long part number for that probe (P/N 765931-1-0).
Additionally, the allowable capacitance range is labeled (45.20 to 50.00). The final label is the associated HI-Z (Hi-Z RT OUTER). The arrow points to the installation position in the wing, with the number of the closest fuel panel access door (10Q is closest to RH DOOR #6.)
The test box cables access the FQMC, located in the aft RH avionics closet.
This allows evaluation of the entire 400HZ capacitance wiring, from the probes, to the wing disconnects, right through the fuselage harness.