connect your indicators straight where you found them.
wires 17 and 18 are negative outputs that, going by what you have written, looks like they become negative outs on arm (when you arm the alarm) - typically used to auto shut power windows on arming - and alarm, which when it is going off. - which could be used for a number of things. (screamer siren etc)
and 18 is to be used to activate a relay which in turn will activate your pager.
in a nut shell the wires go to ground on arming the alarm, and also when it's going off.
sort of make sense?
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