proximity sensor

I have a miata and my friend gave me his old proximity sensor.  I think it's a 508tc.  That's what's on the plastic anyway.

Currently I have a viper 600 installed in my car.  I see the 4 prong hole for optional sensor on the alarm itself.  However, the 508tc proximity sensor only has 3 prongs.  I also dont have the cable that comes with the proximity sensor so I made one up from another older alarm.  I connected the positive and negative to the sensor and the lights blink green and red.  I connected the last prong on the sensor to either one on the alarm itself but it doesn't seem to work right.  I get a chirp but it doesnt go off. 

Any suggestions?

Thanks

Oilver

Look at the downloads section, download the Viper 600 install manual:

page 25:  inputs less than 0.8 seconds will provide the 'warn away' signal .. while inputs longer than 0.8 seconds will trigger the full alarm.

On page 26 is a diagram of how to cut the pre-wired Viper wire and implement the DEI shock sensor.

Hopefully this helps