Symptom		Corrective Action		Remarks
6.	Handset doesn' t ring or external alerter, i.e., sonalert, light does not actuate.	1. 2.	Verify ringer is enabled. Verify CAS outputs are programmed.	Select "9" for "Setup" from Main Menu. Press "3" for info. This screen will indicate if ringer is "enabled" or "disabled". Select "9" for set up from Main Menu. Press "+" for more followed by your Maintenance Passcode, and the "+" for OK. Press "+" three times to get to the Auxiliary Call Alerter screen. Select the device (0-9) to be activated buy this handset. The selected device number will be highlighted and the external alerter will activate.
7.	Cannot make seat-to-seat (in-plane) calls.	1.	Verify "In-plane" is displayed on "Services" screen (when handset is on-hook). You must have two or more phones for "in-plane" to be displayed.	"In-plane" is only displayed when one or more handsets have in-plane numbers assigned to them. Select "9" for "Set-up" from Main Menu. Press "+" for more followed by "0000" (for Maintenance Passcode) and the "+" for OK. Press "4" for phone numbers, then "1" for In-plane. Select desired in-plane number from list (0-9). The current in-plane number will be highlighted.
		2.	Verify an in-plane number has been assigned to all handsets (0-9).
9.	Handset displays error codes or failure indication.	1.	If the fault code is an odd number, cycle power to the system using a 30 second interval between breaker off to breaker on. If error codes or failure indication are still present on handset screen while attempting another call, remove and replace ARTU.	* Allow five minutes for Built In Test to complete. * Refer to ARTU installation and replacement procedure. *Even number faults are recoverable faults (system may recover without power cycling. Hang up handsets and try air-ground call again.) Odd number faults are non-recoverable faults (cycling power to ARTU is necessary for the system to recover).
		2.	For even fault code numbers, hang up all handsets and try the air-to-ground call again. If the fault reoccurs, cycle the power as in Step 1 and try again. If the fault code persists, remove and replace the ARTU.
10.	Cannot access maintenance screens	1. 2.	Contact maintenance crew for passcode. reset passcode to default.	MMTI Software must be used to RESET the maintenance passcode. Select MMT-Installation at start-up option menu. Continue thru automatic tests to display screen #19 to RESET maintenance passcode to factory default.
11.	Handset speaker volume not loud enough/too loud	1.	Handset speaker volume can be raised or lowered independent of the external volume buttons.	Press "9" for setup at main menu. Press "+" for more followed by the maintenance passcode, then "+" for OK. Press "+" 4 more times stopping at the "SPEAKER GAINS" screen. Reduce or increase the coarse adjustment to vary initial off hook speaker volume.