User's Manual

SECTION III OPERATION
SM 7063 07/97 3-26
3.12.4 ALARM Annunciator
The
ALARM
annunciator operates in conjunction with the
ID Code Display
. When a system alarm
condition is initially sensed by the CDU, it will cause the
ALARM
annunciator to flash 5 times together
with a message on the
ID Code Display
indicating the nature of the alarm. This is accompanied by
beeps from the sonalert. The
ALARM
annunciator will then remain ON and the associated message
shown in the
ID Code Display
will alternate every 2 seconds with other existing information (e.g., “ID
Code = #####” then “LOW PRES”, etc.).
The
ALARM
annunciator and related
ID Code Display
message will turn OFF when the condition is
corrected. The types of ALARM conditions are as follows:
1. Low Pressure Alarm:
The Low Pressure Alarm is provided to the locomotive operator as a warning that the brake pipe
pressure at the rear of the train has dropped below a specified threshold (typically 45 psig).
Whenever the brake pressure drops below 45 psig (configurable via the Diagnostic PC), the
ALARM
annunciator will flash ON and the ID Code Display will show
“LOW PRES”
. In addition,
the
Brake Pressure Display
will initially flash 5 times showing the current low pressure value.
2. Valve Fail Alarm:
Two-way End Units incorporate a valve fail detection circuit which checks the integrity of the
components used to actuate main emergency air exhaust valve. The status of the valve fail
detection circuit is transmitted to the CDU in every regularly scheduled message and immediately
upon detection of a valve drive circuit failure.
When a valve failure condition is received by the CDU, the
ALARM
annunciator will flash ON and
the ID Code Display will show
“VALVFAIL”
.
3. No Air Alarm:
In order to conserve battery capacity, some End Units automatically power themselves down after
the brake pipe pressure drops below 5 psig for more than 5 minutes (PC configurable). Just prior
to power down, the End Unit transmits a final message indicating a NO AIR condition.
When the CDU receives a NO AIR message from the End Unit, the
ALARM
annunciator will flash
ON and the
ID Code Display
will show
“NO AIR”
. In addition, the
Brake Pressure Display
will
flash 3 dashes
“- - -”
and then stay steady ON. This indicates that the brake pipe pressure at the
rear of the train in unknown since the End Unit is now in a powered down state.
4. Not Armed Alarm:
If the Arming process has not yet been performed, the CDU will alert the operator that it is in a Not
Armed state, and as such, its Emergency Switch is disabled. The CDU’s
ALARM
annunciator will
flash ON and the ID Code Display will show
“NOT ARMD”
.
In addition, for CDUs equipped with the ARMED Status LED on the Front Panel, this LED will be
OFF as an additional reminder.