Car Audio Display Board Wiring?

How do they wire a Car audio display board for retail store.

Ours at circuit city were pretty basic.  It was a completely modular system that had a bunch of towers.  It's been years since I worked there so some of my info may be a bit off.

Each tower (probably 15 total towers to cover 3 display walls and one display room) consisted of ~12 slots.  In any slot you could insert a card that slid in and had a thumb screw to hold it in.  You could put anyything you wanted inside that slot, as long as you had the right card.  So, if you put a head unit there today, you could put an amp there tomrrow, you would just have to swap the card and obviously wire it up.

We had head unit cards that had speaker inputs and RCA inputs, we had speaker cards (I think they had two inputs but we only used one per side because of the physical distance between the left and right speakers), and there were amp cards (I think they just had speaker inputs).  Every card also had a connector for a switch and an indicator light.

All of the slots were addressed to each tower, so you would have Tower 1, slot 1 through tower 1, slot 12 (or whatever the max was).  You then went to the next tower (ie Tower 2, slot 1 and so on).  Every individual card had a unique addres in the system.

The towers were then ran to a computer (I think we actually had 3-4 computers).  The computers had an interface card of somesort that the towers plugged in to.  We then used proprietary softward to set everything up on the touch screens that were available to the customer.  They made the addressing simple, you just went in to setup mode and click on the address box then pushed the button of the desired speaker and the address was automatically inserted.  You could then put names, sizes, and I think even prices in the computer so the customers could get a bunch of info from the screen.

As far as "how" they actually worked though, I'm not 100% sure.  I believe the audio sources were all routed on the main bus that connected everything together through relays - yet I don't ever remember having any relay problems (and card failures happened very, very often). 

We then used large power supplies hooked to car batteries to run the whole show.  I'm not sure how they kept the power supplies from overcharging the batteries - maybe they just didn't worry about it?  That part has always made me wonder.

All and all, Circuit City used a very flexible system that was well thought out, and when working properly, was really, really cool.  When we started having problems they were a nightmare, especially considering we had no info on them and everything I learned I learned the hard way - trial and error.  By the end of my few years at CC I must say I was pretty good at fixing them!

I figured it out!!