Don't think they discovered the hall effect yet when they made these... Its a VR sensor,
http://en.wikipedia.org/wiki/Variable_reluctance_sensor

I used one of these to convert it to 5V pulses,
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5822/t/al

__________________
Ich liebe meine Autos!

1991 Mercedes-Benz 560SEL | Megasquirt MS3-Pro | 722.6 transmission w/ AMG paddles | Feind Motorsports Sway Bar | Stinger VIP Radar | AntiLaser Priority | PLX Wideband O2 | 150A Alternator | Cat Delete
1981 Mercedes-Benz 300SD | Blown engine, rebuilding someday...
1981 Mercedes-Benz 300SD | Rear ended, retired in garage.
2009 Yamaha AR230HO | Das Boot

Excessive speeding? It ain't excessive till I redline!