Wow, this one's still gray. The ones here are 250 and 400w HPS (split doors here BTW) and all of the paint is long gone.

I'd have to know whether the other lights have P-cells or not. If they do, chances are this one has an Astrodome installed.

It's on a group relay system.

OK, that's called a Remote Control Outdoor Circuit or RCOC for short. Basically, a master P-cell linked to a lighting contactor switch to activate a series of lights. Not a series circuit per se.

I never said it was on a series circuit, I've seen the cylindrical control relay and the PC that controls it on a few poles upstream.

We have older setups in my area that are multiple wired but controlled by 1 PC....(that is for wooden pole mounted ones) They are connected to a relay system that has a special mechanical moving parts inside with a 30 or 60 amp fuse. The photocell just activates a switching system that has magnetic mechanical parts. The photocell is not at all connected to the streetlights, its the magnetic switch that connects and disconnects the row of streetlights.

I've have a close up shot of the relay it's a EPAC Mercury Wetted Relay

Some municipal setups here still use relays but most newer setups now have their individual PCs.

MTO lighting is usually always relay controlled.

I have 3 relays in my collection...2 identical 30 amp ones (almost) and one 60 amp

Interesting, are they the cylindrical version or the boxy version.

Mine is this one but I have seen those cylinder shaped ones in use in my area also. The 60 amp I have is physically bigger and is all cast aluminum instead of the brown plastic (not sure what type of plastic but it looks VERY new inside!

Nice, I don't think I've seen the boxy style here yet, the cylinders are a lot more common here.

This is still there, although the mercs and HPS lights on the side streets have been LED'd.