sundance-communications.com/forum Forums General General Telephone & Systems Information Inside the central office

I happened to be working inside of a central office the other day. All of the equipment, wiring, racks, & batteries are just mind blowing. Not to mention the engineering behind all of it. Anyway, came across a couple things I was wondering if anyone on here would know about.

I was in the equipment room, in what they call the "Frame Area". Basically large racks, close together, with twisted pair wiring, ladders on rails, narrow isles, etc.

First, saw a handwritten sign that read something like "Warning: Purple/gray wire with red caps is 147 volts". Might of been 187 volts, don't remember. Saw wire on the racks that matched the color code and where it terminated had red caps. What could they possibly need 147 volts for? Could this voltage be out in the street and even inside a termination or NID cabinet? Thinking how many of these I've worked in through the years gets me worried!

Second, saw something on the rack that looked like the microphone piece of an old bakelite handset, with a white button to the left and a red light to the right. All mounted to a small board about 3"x5". Any idea what this is?

Item 1 sounds like HDSL, which is most commonly used for T1's. The network transport voltages on HDSL2 are in the 190 vDC range. They will certainly get your attention! Can't help ya with item 2 though.

Any carrier, range extender and other equipment carriers can have high DC voltage. You can always tell a new frameman by the blood on the back of his hands. The mic with the push button and light is (or at least used to be) for talking to the test board when they called you.

The red caps meant Special Circuits, I thought the mic was a test board thing too Bill. We never used it that way (early 70's), we had 2 way speakers and Test board ran the conversation..all we had to do was yell back at em....which was kinda fun at times, glad those conversations weren't taped.

Years ago, when I was a Splicer's Helper, we were changing a Feeder Cable to an Office Building in Downtown Dallas.

They sent me (THE ROOKIE AT THE TIME) up to move a jumper from one BP (Binding Powst) to another.

The client was a LARGE power company, and the jumper I was moving was a "TELEMETERING" circuit, unknown to me.

So, the rookie I was, leaned on the METAL FRAME of the rack that all these cables came into, and using my NON-INSULATED Needle Nosed Pliers, reached over to remove the jumper.

Had to be even more voltage than a RINGING MACHINE!

So, 40 years later, I found out that HDSL Circuits can KICK LIKE A MULE as well.

You should have had a Switchman give you a tour.

Although now, you can't follow how a call flows like we could in the old STEP BY STEP days.

Yes, the RED BUTTON & Hadset was a RING DOWN to the Test Board.

HDSLs can really bite ya! That's quite interesting merlinman. I've never been around a step-by-step..I'd really like to hear more sometime! I got started as a frame tech and learned some AG GTD-5 maintenance (with the huge reel-to-reel MTUs.) Notifier, Welcome to the Board! At least they posted hand written signs, and used the red caps! If you get back to that CO, like merlinman said, ask those techs to give you a tour.

Bill, That was me with the scraped up knuckles. I also had a nice collection of bite marks on the back of my forearms, until I learned about the longer size bits and sleeves.

Interesting stuff!
I was in a phone room at a large office building today. On the wall, someone wrote 'go by CA and PR, not BP!' I assume that means cable and pair, not binding post?

That mic, button, and light connected to a frame talk circuit that was connected to the "Local" test board. There are no more "Local" test boards so the equipment is not needed anymore. Each mic was a station on the cirucit. When the test board connected to the circuit it would activate some speakers on the frames in the CO. The tester would callout for a tester to answer by calling "Hello Central" or whatever the name of the office was. Some times the tester would be on the wrong circuit and the office tech would have to tell the tester he was in the wrong office. When the tester called, all of the Red lamps would come on. The office tech would press the white button to activate the mic where he was standing. all active mics whould have the red lamp flashing. Non active mics would have the red lamp on steady. I hope this answers your question.

Purple/Gray is not a stander AT&T color. HDSL and T1 Spans are run with Purple/Red Tight twist wire on the frame.

Around here the local at&t guys use the purple/gray for the DSL on the SNI to DSL filter.

Ah, yes, the good old days, indeed. Squawk box technology has really changed.

Jeff, a small SXS office (3800 lines) would produce a 85-118 db noise level during slow periods. Just like a WWII German machine gun. And if one was just a bit out of adjustment you could hear it.

Those were the days, ala Archie Bunker.

Silence in the older offices was not something you wanted to hear.