Tyco MX4428 - Manual (Page 71)

Document: LT0273 MX4428 MXP Engineering / Technical Manual
Analog Loop Design Considerations
Issue 1.5 24 March 2006 Page 4-3
4.2 ANALOGUE LOOP/LINE LAYOUTS
4.2.1 LINE MODE
The MXP is designed to run in LOOP mode only. The dual line mode of the MPR is not
supported. However a star configuration can be used, refer to section 4.2.3.
4.2.2 LOOP DESIGN WITH SHORT CIRCUIT ISOLATORS
There are two main reasons for using isolator bases on the analogue loop.
(i)
When the MXP powers up a line/loop, it will only have to power up one section of the
line/loop at a time, reducing the power required by the MXP from the MX4428 supply
loop during startup.
(ii)
If the loop is shorted then the MXP will loose communication with only those devices
on the shorted section between 2 isolators. If every detector was mounted on an
isolator base, then all detectors would remain functional in the event of a single short
circuit.
Refer to Figure 4.1 for an example of loop wiring with Isolator Bases.