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XP95 20D ISOLATING BASE
OPERATING
PRINCIPLES
The XP95 20D isolating base
senses and isolates short
circuit faults on XP95 loops
and spurs. The base is loop
powered, polarity sensitive
and accepts the XPERT card
to set the associated device
address.
In short circuit conditions
the integral yellow LED is
illuminated. The detector
associated with the base
remains active under short
circuit conditions. Power
and signals to the affected
section are restored
automatically when the
fault is cleared.
ELECTRICAL
DESCRIPTION
Under normal operating
conditions, a low impedance
is present between the –IN
and –OUT terminals of the
base, so that power and
signals pass to the next
base in the line.
If a short circuit or abnormally
low impedance occurs, the
fall in voltage is sensed and
the base isolates the negative
supply in the direction of
the fault.
In applications where it is not
necessary to use an isolating
base for each detector, up to
twenty devices (detectors
and XP95 interfaces) may be
installed between isolating
bases, provided that their
total switch-on surge current
does notexceed20mA.
Circuits may include spurs,
which should be connected
between the spare –OUT
terminal and the base L2
terminal. Spurs connected
in this way appear directly
across the loop on the
output side of the isolating
base. Short-circuit faults
on the spur therefore short
circuit the loop and vice
versa. The effect of such
short circuits must be taken
into account in the system
design and may require the
use of extra isolating bases.
For further information on
the use of XP95 isolators,
please refer to PP2090 Short
Circuit Isolation in XP95
and Discovery Fire Systems.
TECHNICAL DATA
XP95 20D Isolating Base
Device Part No:
45681-284
Maximum Loop Operating
Voltage:
28V DC plus 9V protocol
pulses
Minimum Normal Loop
Operating Voltage:
17V DC
Power-up Time:
>10mS
Isolation time, 2Ω load at
28V:
20µs
Isolation Voltage:
14V
Isolation Indicator:
Yellow LED, lit continually
in isolation condition
Current Consumption:
at 18V 23µA
at 28V 43µA
at 18V and adjacent
sector isolated 4mA
Maximum Line Current:
Non-isolatingcontinuous1.0A
Transitionintoisolation 3.0A
On Resistance:
<0.2Ω
Device Reset Resistance:
300Ω
EMC:
S
ee page 21 for full details
Operating Temperature:
-20°C to +60°C
Storage Temperature:
-30°C to +80°C
Relative Humidity (no
condensation/icing):
0% to 95%
Dimensions:
100mm (diameter) x 24mm
(height)
100mm (diameter) x 60mm
(height) base with detector
fitted
Weight:
100g
XP95 20D Isolating Base ▲PartNumber45681-284