Garage door sensors

Hi, guys. I have garage door obstruction transmitting and receiving "eyes" that I was given. How would I go about reading the receiving eye?

There must be a huge number of possible configurations for this - my garage sensor for example uses a passive reflector one side and an IR transmitter and receiver the other. It apparently has a relay inside (it clicks) so it would be trivial "read". It also lights an LED when the beam is unbroken so if nothing else I could simply measure the voltage across that LED.

However, I have absolutely no idea how your garage "eyes" work so I can't really help.

Assuming you don't have a part number, do you at least have an idea of how they were wired up to work and what happens to them when they do? Do you have any idea of what connections are present on each part? Rather more information would be helpful.