Where do I have to start? - RPM reading and action at certain engine speed

Hey Guys,

Do not let you hear anything for a while.

The engine cut-off I could probably obtian with the some digital output switches (feature of the engine dyno) and a relay.

Xensor also sent me the pinout of the sensor:
Black = - signal
Clear = + signal
Yellow = ground

When I have to translate this to the Arduino, I have to make the following connections I think:
Black to digital input
Clear to +5V
Yellow to ground

Could anyone confirm this? About the black one (- signal) I am not really sure I could connect this to a digital input.