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MX4428 MXP Engineering / Technical Manual Document: LT0273
MXP Loop Filter Board
Page 10-2 24 March 2006 Issue 1.5
10.1 USE OF MXP LOOP FILTER BOARD
Some field problems have occurred with the MXP detector loop picking up interference from
adjacent or nearby wiring, resulting in faults and possibly prealarms. The “MXP Loop Filter
board” (part number PA1038) is now available and it can easily be fitted to an MXP in order
to remove the interference and restore normal operation.
One or more of the following symptoms may be evident –
1. Intermittent “scan fail” faults.
2. Intermittent unexpected Prealarms.
3. The MXP diagnostic port “Total reply fail count” is much higher than expected
(normally you should get less than 1 per hour).
4. The above problems occur in time with some external event e.g. lift motors running,
radio transmitters operating etc.
Note that symptoms 1 – 3 above can also be caused by other factors e.g. the loop has too
many devices connected or is too long. The MXP Loop Filter board will not help if this is the
case.
10.2 FITTING
Remove the loop wiring from the MXP. Fit the filter board in the loop wiring terminals of the
MXP. Then fit the loop wiring to the filter board. Refer to Figure 10.1.
Figure 10.1 MXP Loop Filter Board Fitted to an MXP