User's Manual
ADCP-75-110 • Issue 2B • July 2001
Page 5
©
2001,
ADC
Telecommunications,
Inc.
1.2.3 Fault Detection and Alarm Reporting
The
DHU
is
designed
to
detect
internal
circuitry
faults
and
optical
port
faults.
Various
front
panel
Light
Emitting
Diode
(LED)
indicators
turn
from
green
to
red
or
yellow
if
a
fault
is
detected
or
an
optical
input
is
lost.
A
set
of
alarm
contacts
(normally
open
and
normally
closed)
are
also
provided
for
reporting
an
alarm
to
an
external
alarm
system
when
a
fault
is
detected.
Both
major
alarm
(all
fault
conditions
except
high
temperature)
and
minor
alarm
(high
temperature
fault
condition)
contacts
are
provided.
1.2.4 RF Signal Connections
The
RF
signal
connections
between
the
DHU
and
the
BTS
are
supported
through
two
type
N
female
connectors.
One
connector
is
used
for
coaxial
cable
connection
of
the
forward
path
RF
signal.
The
other
connector
is
used
for
coaxial
cable
connection
of
the
reverse
path
RF
signal.
In
most
installations,
the
DHU
will
not
connect
directly
to
the
BTS
but
will
be
connected
to
an
interface
device
such
as
the
RIU
or
the
LIU.
Additional
information
concerning
the
DHU
to
BTS
interface
is
provided
in
the
Digivance
ICS
Remote
Interface
Unit
User
Manual
(ADCP-75-113)
and
in
the
Digivance
ICS
Local
Interface
Unit
User
Manual
(ADCP-75-114).
The
DHU
requires
a
composite
forward
path
RF
signal
level
of
–20
dBm
or
lower.
An
overdrive
limiter
protects
the
system
against
excessive
inputs
but
does
not
function
during
normal
operation.
The
DHU
does
not
have
Automatic
Gain
Control
(AGC).
1.2.5 Optical and Electrical Interface Connections
Operation
of
the
DRUs
and
DEUs
is
supported
by
six
optical
and
six
electrical
ports.
Each
optical
and
electrical
interface
connection
includes
a
status
LED,
a
small
form
factor
LC
type
optical
transceiver,
an
RJ-45
DC
power
jack,
and
a
port
enable/disable
switch.
An
optical
port
may
be
connected
to
a
DRU,
a
DEU,
or
not
used.
An
electrical
port
may
be
connected
to
a
DRU
or
not
used.
Unused
ports
require
no
connections
at
all
and
are
disabled
via
the
corresponding
port
enable/disable
switch.
When
disabled,
the
port
LED
is
off,
the
alarm
reporting
function
is
disabled,
the
laser
is
off,
and
the
DC
power
is
off.
Enabling
the
enable/disable
switch
activates
all
functions.
1.2.6 Powering
The
DHU
is
powered
by
120–240
Vac
(50–60
Hz)
power
which
is
supplied
through
a
standard
three-conductor
AC
power
cord.
The
power
cord
is
provided
with
the
DHU
and
is
98
inches
(2.5
meters
)
long.
A
resetable
circuit
breaker/On-Off
switch
is
provided
at
the
unit
front
panel.
The
switch
applies
power
to
the
DHU
internal
power
supply.
1.2.7 Cooling
Continuous
air
flow
for
cooling
is
provided
by
dual
fans
mounted
on
the
right
side
of
the
housing.
A
minimum
of
3
inches
(76
mm)
of
clearance
space
must
be
provided
on
both
the
left
and
right
sides
of
the
DHU
for
air
intake
and
exhaust.
An
alarm
is
provided
that
indicates
if
a
high
temperature
condition
(>50º
C/122º
F)
occurs.
The
fans
may
be
field-replaced
if
either
fan
fails.
1.2.8 User Interface
The
DHU
user
interface
consists
of
the
various
connectors,
switches,
terminals,
and
LEDs
that
are
provided
on
the
DHU
front
panel.
The
DHU
user
interface
points
are
indicated
in
Figure
3
and
described
in
Table
1.