User's Manual

SECTION III OPERATION
SM 7063 07/97 3-28
3.14 COMMUNICATION TEST
If radio communications problems are suspected, the front-to-rear and rear-to-front radio links may be
tested by momentarily pressing the
COMM ARM
key.
When the
COMM ARM
key is pressed, the
Function Menu Display
shows:
" WAITING FOR REPLY "
for 2 seconds. Depending on the status of the reply, one of the following will be displayed:
1. If the Communication Test is
successful
, the
Function Menu Display
shows:
" COMM TEST OK "
for 2 seconds and then reverts to the currently active menu item. In addition, the
Message Receipt
Indicator
in the Brake Pressure Display will blink ON to indicate that a valid message has been
received by the CDU.
2. If the Communication Test
failed
, the
Function Menu Display
shows:
" COMM TEST FAILED "
for 2 seconds and then reverts to the currently active menu item. In this case, the
Message Receipt
Indicator
in the Brake Pressure Display will NOT blink ON since no valid message has been received
by the CDU.
3.15 AUTOMATIC COMMUNICATION TEST
The CDU automatically checks the radio link on a periodic basis. It sends a status update request
message to the End Unit every 10 minutes. The purpose is to test the front-to-rear radio link. If the
End Unit replies immediately, no indications are displayed on the CDU front panel. If a reply is not
received, the CDU send another request 15 seconds later. If there is no response to this retry, another
transmission is made in 6 minutes. If there is no response to this request, a final transmission is made
15 seconds later. Finally, if the End Unit does not reply to this last request, a
F TO R FAILURE
ALARM is declared and displayed on the CDU front panel.
The Automatic Communication Test is performed in the time periods described to allow recovery from
radio link “black outs” due to tunnels and certain terrain conditions. The total time to the declaration
of a
F TO R FAILURE
ALARM is 16.5 minutes.