garage safety sensor

I am in the process of building a web controlled garage door opener and i'm having an issue. I have built the circuit to actually open and close the door. now I am trying to add the safety function to the circuit. I want to be able to read the safety device with the arduino.

The safety sensor sends a pulse signal to the garage door motor every 6ms.

how would i go about sensing this signal with the arduino?

What do you mean it sends it?- down a wire?- radio? What kind of pulse?- eg what voltage is it and what's its duration?

I'm thinking just a digitalRead() inside loop()?