Ford Mustang factory alarm disarm

When disarming  the Ford OEM alarm on a 2000 Ford Mustang, (Dr GREEN/ Purple) is it a pulsed -'ve or constant? The alarm/remote start I am installing does not have a output wire for disabling the factory alarm, so I a thinking of tapping off the remote start IGN or ACC wire to send the -'ve signal when it tries to do a remote start. This would however be constant -'ve as long as remote is operating. If I need pulsed output, how would I go about doing that?

Thanks

I am installing a VSAS 2 way remote start (Guardian) that a friend of mine bought off ebay. Took me 2 hours to decipher the english. I can only get the unit to engage ignition/acc  wires, but not the starter wire. However, if I try a remote start (which turns on ignition, then fails) then turn key to ON position, the remote unit cranks it over to start and it will then stay running.

There is no disarm wire. There is a white ACC wire, which it uses to sense the ignition on. I tapped that into the same wire that the relay uses from the ignition.

I have place a transponder next to the ignition and I am using the blank key for now as to not send confusing codes to ignition.

ANOTHER QUESTION:  The transponder, if I place it next to the ignition without any wires wrapped around it ( one suggestion to use a relay, transponder and wire loops to fake a key) it senses the correct code. As soon as I place the transponder with wire wrapped around it, it detect a bad key. Anyone had success bypassing transponder with relay/transponder method?

Thanks