Backplane Connections - ADC HRE-425 List 1 Quick Installation

B
ACKPLANE
The HRE-425 List 1 backplane
•
wire-wrap connections to each of the 12 card-edge connectors (J1 through J12)
•
terminal block connections to TB1
•
25-pair, multiple connectors (P1, P2, P3, and P4)
P1 P3
P
OWER
Each of the 12 slots are equipped with a 0.5A fuse between the -48 Vdc shelf supply and
pin 35 as shown in Figure
requirements when using the HRE-425 to house doubler or remote units.
All the fuse alarm contacts are transmitted together on one bus and connected to the Fuse
Alarm, pin 3 of TB1. If a fuse opens, the normally floating Fuse Alarm in pin 3 drives to
-48 Vdc.
When slot 12 is used for an internal -48 Vdc shelf supply, fuse F12 becomes the shelf fuse
and must be replaced by the 2A fuse included in the installation kit. If F12 opens in this
application, the Fuse Alarm is left open and will not be driven to -48 Vdc (as would be the
case if an external power supply were lost).
The internal supply in slot 12 is limited by 2A fuse F12 in order to be compatible with the
maximum current rating of typical, 400 mechanics shelf supplies. This 2A capacity is
sufficient when HRU remote units are used in the other 11 slots but not when HLU-431 line
units are used. An external power supply rated at a minimum of 5A is required to provide
adequate power to a shelf full of HLU-431 line units operating under maximum load. See
the HLU-431 technical practice for additional information.
Properly ground the HRE case to avoid shock hazard to craft
personnel, bit errors due to noise and crosstalk, and damage
to HRU circuits. ADC recommends that pin 4 of TB1, frame
ground, be connected to earth ground.
The HRE-425 List 1 provides access to frame ground on pins 1
and 27 of each slot connector.
C
ONNECTIONS
(Figure 3) can be connected in one of the following ways:
J12-J1
P2 P4
Figure 3. HRE-425 List 1 Backplane
F
USES AND
4. This accommodates the maximum power consumption
TB1
G
ROUNDING
Fuse 1-Fuse 12
H0330-A