User Manual

P B L Tunnels Loc 2 Units 1 & 2 + 800MHz BDA
Maintenance Handbook
H/book Number:-60-056100HBKM
Issue No:-1
Date:-13/02/2003
Page:-61 of 61
5.1.8 24V Single Relay Board (80-008902)
5.1.8.1 Description
The General Purpose Relay Board allows the inversion of signals and the isolation of
circuits. It is equipped with a single dual pole change-over relay RL1, with completely
isolated wiring, accessed via a 15 way in-line connector.
The relay is provided with polarity protection diodes and diodes for suppressing the
transients caused by "flywheel effect" which can destroy switching transistors or induce
spikes on neighbouring circuits. It’s common use is to amalgamate all the alarm signals
into one, volts-free relay contact pair for the main alarm system.
Note that the board is available for different voltages (12 or 24V) depending on the type
of relay fitted at RL1.