User Manual

PBL UHF 1 & 2 Air Interface
Maintenance Handbook
H/book Number:-60-055900HBKM
Issue No:-1
Date:-13/02/2003
Page:-56 of 56
5.1.9 Single & Dual 24Volt Relay Boards (20-001602 & 80-008902)
5.1.9.1 24V Relay Boards (20-001602 & 80-008902) Description
The General Purpose Dual Relay Board (20-001602) allows the inversion of signals and the
isolation of circuits. It is equipped with two dual pole change-over relays RL1 and RL2, with
completely isolated wiring, accessed via screw terminals.
Both relays are 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
relays fitted at RL1 and RL2.
The single relay board (80-008902) is electrically identical to the dual version but is
proportionately smaller in size. It also has a single in-line IDC connector in place of the screw
terminal blocks of the dual model and performs similar summary alarm functions.