The VOR/ILS control unit is located on the radio and navigation control panel. The control has two dual-function control knobs to energize and control the operation of the equipment. When a localizer frequency is selected as shown in the frequency digital display window, the corresponding glide slope frequency is automatically selected. The function of the controls is as follows:

a. The rear portion of the selector marked “OFF/PWR/TEST” selects the MHz section of the desired frequency for a VOR or ILS function in 1 MHz steps.

b. The rear portion of the selector marked “VOL” selects the kHz section of the desired frequency for a VOR and ILS function in 50 kHz steps.

c. The front portion of the selector marked “OFF/PWR/TEST” energizes the ARN-127 when selected to PWR, and in the TEST position provides the capability for VOR circuit testing.

NOTE

There is no self-test function for the ILS circuit.

d. The front portion of the selector marked “VOL” controls the VOR/LOC audio level.

e. A switching matrix (Figure 1-11-19) is provided to assist in determining the control functions of the NAV SELECT, COURSE CONTROL LIGHT SWITCH, and the ID-351 information provided.