PM4/8/12/16 & PM4/8-SA Installation and User Guide v1.1
32
The external message trigger inputs should ideally be connected to volt-free switch
or relay contacts, which may be either NO (normally-open) or NC (normally-closed).
This choice is set by moving J20, J21, and, (on the PM8-SA only), J22. The three
jumpers allow selection of NO or NC independently for: M1 and M2; M3 and M4; M5
to M8 (PM8-SA only). See “PCB layout diagrams” on page 49 for location of the
internal jumpers. The triggers are momentary – i.e., the external contacts need only
to close (NO) or open (NC) briey for the message to be initiated.
Connecting the trigger inputs to equipment with open-collector outputs is also
possible, but we recommend that all the equipment involved is located as close as
possible to the PM-SA rather than distributed around the building. This is because
connecting the PM-SA’s common 0 V to items of equipment running on widely-
separated AC mains outlets can frequently be problematic. The trigger inputs are
diode-clamped, and may be connected to open-collector outputs with Vcc voltages of
up to +24 V.
Note that the external commands do not directly trigger the individual message
stores, but the zone groups A to D (PM4-SA) or A to H (PM8-SA). This is because
triggering a stored message is of little use unless one or more destination zones are
also dened. The SA models of the PM allow each zone group to have any of the
stored messages assigned to it; thus an external trigger causes the message assigned
to the particular group to be broadcast to the zone(s) belonging to that group. See
“Assigning a chime to a zone group (SA models only)
” on page 34 for more
details.
When all the connections have been correctly made, tighten the locking clamps on
the cable glands to ensure that no strain is placed on the terminals if the external
cables are tugged or stretched.
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