These were also in the building. Some sort of “emergency alarm” for the telephone company. For those of you unfamiliar, “Bell System” was the old term for the telephone company. These were not connected to the fire alarm panel. But the telephone company monitors itself at a central location, I imagine these report to that central location to let them know there is a situation in the building and dispatch help. Maybe even a sort of early panic alarm.
We actually ended up burning up one of the EOL resistors on the horn circuit. It takes a 5 Watt resistor (typical EOL resistors on NAC circuits are 1/4 to 1/2 Watt) and someone along the line replaced the original resistor with a 1/4 Watt. Well, when we rang the horns, that little resistor couldn’t handle the current I guess and it burnt up! Of course, our contact there says “Yeah, the last couple of times we’ve had a problem with that”.
But going through the telephone company central office is interesting in itself. Just the massive amount of equipment, wiring, electronics, etc they have there can make an electronics geek like myself go nuts! The battery area is a little scary. Sort of look like clear 5 gallon buckets all interconnected supplying 48 Volts DC on “unfused” buses. You think getting shocked by a car battery was bad, hate to think what could happen to a person from these!
Here’s a picture of the battery area (not the one I was at on Friday, this is from another site but the same idea). The metal bar on top of the batteries is what’s carrying the current between them. You definitely don’t want to touch that!