What activates the ADF system?

What activates the ADF system?

• A. The ADF power switch
• B. The ADF on signal (ground)
• C. The RMI keypad input
• D. The altitude hold switch

Answer: (B)

Activation comes from the ADF on signal, which is a ground input that enables the ADF receiver. Even if power is available, the ADF stays off until this on-signal is asserted, turning the ADF circuitry on so it can receive bearing information from the loop and sense antennas and display it on the RMI. The other options don’t actually turn the ADF on: simply applying power via a switch may power the unit, but the on signal is what gates its operation; the RMI keypad input selects or interacts with the display but doesn’t power or enable the ADF; the altitude hold switch is an autopilot control and has no role in activating the ADF.

Activation comes from the ADF on signal, which is a ground input that enables the ADF receiver. Even if power is available, the ADF stays off until this on-signal is asserted, turning the ADF circuitry on so it can receive bearing information from the loop and sense antennas and display it on the RMI. The other options don’t actually turn the ADF on: simply applying power via a switch may power the unit, but the on signal is what gates its operation; the RMI keypad input selects or interacts with the display but doesn’t power or enable the ADF; the altitude hold switch is an autopilot control and has no role in activating the ADF.