P
AGE
6
46131-0598 <90-00018>
P
USH
B
UTTONS
AND
LED D
ISPLAY
On the front panel are five push buttons and five seven-segment
LED displays. They:
♦
Show if there are alarms or failed TBOS displays.
♦
Indicate if the TBOS interrogator ports are transmitting and
receiving data.
♦
Reset the APU’s microprocessor.
♦
Acknowledge alarms.
♦
Indicate alarm location.
P
OWER
The APU operates on -21 to -56 VDC applied at a connector on
the front panel. Power goes through fuse F1 (two amperes) to an
on-board power supply. Power also goes to wire-wrap pins 54
and 56 of connector P2. Use pins 54 and 56, which are limited to
15 mA of current, to provide power to alarm inputs 25-32.
If the fuse fails, the fuse alarm (FA) LED on the front panel
lights. A relay also operates an external alarm.
CIRCUIT DESCRIPTION
INSTALLATION
T
his section describes those steps necessary to install the
46131 APU. These include Equipment Mounting, Switch and
Strap Settings, Wiring, Configuration, 202 Modem Checkout,
and Troubleshooting.
E
QUIPMENT
M
OUNTING
Brackets on the side of the shelf are installed for mounting the
APU in a 19-inch equipment rack. Refer to Fig. 2 for overall
dimensions of the APU.
♦
For mounting in a 23-inch equipment rack, remove the
brackets and reinstall them with the long sides extending out
from the shelf.
♦
For flush mounting, remove the brackets and reinstall them
with the mounting ears even with the front of the APU.
♦
For wall mounting, replace the brackets with special wall
mount brackets furnished as loose parts. The long side of
each bracket mounts to the APU.
NOTE:
The special brackets are supplied only when specifically
ordered. Refer to the Ordering Information section.
W
ARNING
:
When power is applied to
the APU, negative battery
voltage is present at pins 54
and 56 of connector P2 and
at any alarm inputs wired
to negative battery. For
safety, cover these pins
with protective insulation.
Keep the plastic front panel
cover closed during normal
operation.
