If you don't get an answer here, try the Carnetix page. They have forums, including the P1900 and they can probably give you an accurate answer.
I am thinking about getting a Carnetix 1900 psu to put it in my current setup. In the carnetix manual, there is a connection for pulse start, which can be use to start up the computer with a pulse. Its saying that it could be connect to car alarm's auxiliary output or some other unused channels to power it up. I have two questions regarding my current Viper 790VX 2-way alarm. I couldn't completely understand this alarm diagram. What signals (pulsed signal, latched signal, or (-), something else) does it send out if i am going to use channel 4 or auxiliary channel or other unused channels? Which pin of the alarm harness should I hook up the pulsed start wire to?? is there any relay or circuit might needed? Let's make it simple, how to wire pulse start to this alarm? Currently, there are only 4 functions is programmed in my beeper, open, close, remote start and panic.
Holux GPS Iguidance 3.0
7" Xenarc Touch Screen
Carnetix 1900 Power Supplied, Wireless b/g
I'd love to provide some guidance, but I don't have a clue what the Viper inputs/outputs do. But since there are so many of them, I would be surprised if you can't find something (perhaps thru experimentation) that could feed the Pulse Start input to the P1900. As we discussed over in the CarNetix forum, the Pulse Start takes either a momentary +12V signal or a momentary contact-closure signal. Hopefully someone on this forum can lead you thru the Viper I/Os.