Author Topic: Central Office Frames & Jumpering Discussion  (Read 1980 times)

Offline AE_Collector

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Central Office Frames & Jumpering Discussion
« on: January 03, 2014, 06:53:58 PM »
From the topic link below it looks as though a CO Frame discussion topic might be in order.
http://www.classicrotaryphones.com/forum/index.php?topic=10825.0

CDF=Combined Distributing Frame
IDF=Intermediate Distributing Frame
MDF=Main Distributing Frame

Not certain if CDF's were common in other than smaller SxS offices but we had LOTS of SxS here in BC so we had lots of CDF's as well. When I say "We" I mean we in the British Columbia Telephone System - Canada.

All of our larger SxS CO's had an MDF and an IDF rather than a single CDF.
The MDF jumper connected Line Finder to Cable Pair / Protector.
The IDF jumper connected a Line Finder terminal to a Connector terminal thus assigning a phone number to a "dial tone" circuit.

We tended to call all terminals in the field that were in buildings as opposed to on poles or at the side of the street - House Terminals or HT. The main entrance cable to a building was numbered as HT xxxx. xxxx was a number assigned to the terminal that didn't conflict with any other terminals within the same CO area.

We modified HT to EPHT which stood for Enter Phone House Terminal for terminals that had an Enterphone system, primarily Multi Unit Residential Buildings. This identified a terminal that required all main phone lines to individual suites be jumpered through the Enterphone equipment.

Outside we had RA's (Ready Access Terminals) on cables up poles. In most RA terminals one had to connect a pair of wires into the correct pair of the cable passing through it. The pair of wires were called fuse links as they were a softer copper designed to be the first thing to melt if high voltage / lightning was on the circuit. These fuse links were attached to binding posts in the RA and the drop wire would be connected to the binding post that had the fuse links connected to it that you just connected into the correct pair of the cable. Hope that makes sense!

We also have upside cross connect boxes usually along the side of the road but smaller ones can be mounted on poles at convenient working height from the ground. We called these boxes SAC (Service Area Concept or Service Area Cross connect) boxes but i know that in Alberta they called them JWI's (Jumper Wire Interface). These cross connects are jumpers to connect the main CO cable to what we called an FX (foreign Exchange) cable pair. A bit of a misleading term as FX just meant a pair that does NOT go all the way back to the CO. Other companies might call the CO cable an "F1" (Field 1) cable and they are jumps red to a F2 in a cross connect box and maybe an F3 further out before getting to the service address.

Terry
« Last Edit: May 05, 2014, 06:39:14 PM by AE_Collector »

Offline Weco355aman

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Re: Central Office Frames & Jumpering Discussion
« Reply #1 on: January 04, 2014, 01:11:33 PM »
The term IDF and MDF are used in both key systems and Central office. (USA) that i know about.
CDF was only used in Central office. All of the small Central offices 10,000 lines or less
had CDF. The large C.O.'s had TIDS (Toll Intermediate distubing frames) This had trunks and toll
equipment connected to it, also toll switchboards.
Phil

Offline Fabius

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Re: Central Office Frames & Jumpering Discussion
« Reply #2 on: April 20, 2014, 11:48:59 AM »
During my time with New York Telephone in NYC was when I worked in large COs with IDFs. With GTE small sxs offices had MDFs and where identified as such on office diagrams.

Triva: I worked in the Bridge St CO in Brooklyn which I was told was the largest CO frame in the universe. The frame wire runs were so thick that we used splicer tone sets to trace a wire.
Tom Vaughn
La Porte, Indiana
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Offline AE_Collector

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Re: Central Office Frames & Jumpering Discussion
« Reply #3 on: May 05, 2014, 01:23:23 AM »
We had one of those here as well Tom. Our main downtown Vancouver CO known as MUtual (68). Too many exchanges in the same building thus too many tie pairs between them on the frames. Sometimes the only way to trace a jumper was to pull t until it broke and wait for the repair call to come in.

Electronic COs went a long way to fix these problems since a piece of line equipment could be programmed to be a number close to the cable and pair on the frame that it needed to connect to. We called it the "Short Jumper Concept". This eliminated miles of jumper wire on the frames.

Terry

Offline Fabius

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Re: Central Office Frames & Jumpering Discussion
« Reply #4 on: May 05, 2014, 08:51:15 AM »
With the intro of electronic/digital switches and the ability to turn service on and off in the switch came the LIJ concept, left in jumper.
Tom Vaughn
La Porte, Indiana
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ATCA #765
C*NET 1+ 821-9905

Offline AE_Collector

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Re: Central Office Frames & Jumpering Discussion
« Reply #5 on: May 05, 2014, 05:27:54 PM »
We had a "Life" program on the CO Main Frame in the SxS days. I never thought about it before but likely the word LIFE was really an acronym for Left In Frame Equipment or something close to that.

It involved leaving jumpers in place and I am trying to recall exactly how it worked. I think we left the Cable pair connected to the Line Finder on the Main Frame and put in a special colored protector module that likely protected the cable pair but did not actually connect the pair to the finder thus no dial tone in the field. The Intermidate Frame jumper (in a SxS office) which connected the Line Finder terminal to a Connector terminal was removed.

When a request for service at the "Lifed" location came in the protector module was changed to give dial tone and only one jumper had to be run to give them a phone number. Of course the whole circuit could have been Lifed but there would have been a large percentage of times that the phone number (Connector Number) had already been previously removed to move the number to a different address OR we would have wanted to keep intercept on the old disconnected number for a longer period of time.

Terry
« Last Edit: May 05, 2014, 05:36:34 PM by AE_Collector »