I have this unit which I installed many years ago in a new fast food
business. The restaurant failed shortly after it was installed and I
got the equipment back. So in essence it is like brand new.and was
operational when it was removed from service.

The unit is a self contained box with loop sense wires and isolated
spdt relay wires. It operates from 120V. The loop was buried in the
driveway and so I was unable to retrieve that part of the system.

Installation was rather simple. Unfortunately I can't find the
installation instructions however I do recall that we had to cut the
asphalt driveway and bury a loop of AWG. 14 cable. The loop would
sense a large mass of metal over it such as a car, (as opposed to a
non metallic mass), at a drive through and operate a form C relay. I
would like to set this unit up in my own driveway now however the
problem is I don't remember the configuration of the loop, IE how many
turns there were in the loop or its diameter. Actually I think that we
buried it down 8 inches or so and that it was rectangular shaped but
I'm just not sure.

There is no longer a listing for Detector systems however the strange
thing is the number 917-1 does come up as some kind of driveway sensor
but I can't seem to find any information on it.

I would think that this type of unit must be similar to those that are
used at intersections for traffic light control but I'm not sure how
to find that information.

Does anyone have any experience with this type of sensor who can
advise me as to the sense loop characteristics? Thanks for any
assistance, Lenny