ADT Alarm

I'm trying to read the sensors off my ADT Vista 20p control box in parallel with the box. When I tap the zone 1 reed sensor at the Hi part to a digital port and the low part of zone 1 to the Gnd it effective shorts the sensor and bypasses it.

Does anyone have a wiring diagram to monitor the sensor in parallel with the box?

Try using an analog input, but first test to make sure that the voltage never goes above 5V.