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#571733 05/15/14 12:59 AM
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dexman Offline OP
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This topic is a spinoff from a post in the pictures of ugly cabling topic.

I have a couple of pieces of lead jacketed cable. The conductors have pulp insulation.

One thing I've noticed is that the color code on the insulation is just about impossible to decipher.

Bill mentioned that there was no color code (at least a code like we know today).

How did field technicians work with this type of cable if there were no base/stripe colors imprinted on the insulation? It does appear that some of the insulation is dyed.

I used a rotary pipe cutter to cut the lead jacket. It does a good job...as long as I don't tighten down too tightly on the cable.





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If the cable is more than 100 pairs, then it is laid up in groups of 50 pairs. Each group is made up of pairs that are all colored the same. For instance, natural (white-ish) is the tip, and the other color is the ring.

When splicing, "random" splices are made, making sure that at each intermediate splice along a run, the groups (but not the individual pairs within the group) are mated properly. At these splices, all 50 pairs in a group are mated with 50 pairs of the equivalent group in the adjoining section. At the CO end, and the terminal end, a talk pair is established, and a person at each end wearing a headset determines the individual pairs, by sending tone back and forth. That is when the numbered pair code is created.

As each pair is identified, the splicer pushes the pair of wires through one of 50 numbered eighth-inch holes in a linen tag, called a "board." This process is called "boarding the group."

The groups:

When the sheath is cut off, and housekeeping is taken care of (bonding, grounding, wrapping the "choke" of the cable with tape to prevent abrasion, separating and identifying the groups of 50 pairs, etc) the splicer uses a code that is created by the colors of the groups.

Holding the end of the cut cable, you will see that the groups of 50 pairs are all natural (white) and a color. But, there is only one group that is colored with white/green pairs, in each concentric ring of groups. That group is counted as number 1.

The adjacent groups are labelled with numbered tags or tape, or colored tie-wraps, as follows:

If you are facing the Central Office, the groups are numbered COunter-clockwise. If you are facing the "Block" (field) you count Clock-wise. The mnemonics are "CO = COunter" and "Clock to the Block".

If there are so many pairs that the cable has more than one layer of 50-pair groups, then you start over, looking for the one white/green group in the next layer inside. The clock/counter clock counting is the same in every layer.

Because pulp cable is prone to faults during manufacture, the factory tests each pair, and attaches a tag that indicates how many faults (generally, opens) that exist and in which groups they are. The maximum allowable percentage of faults is 1% per 900 feet of cable.

There are "interstitial" pairs that are laid up, singly, in the spaces (interstices) between the groups. These pairs are colored in strange but distinctive ways: red/black, yellow/black, red/yellow, green/black, etc. They are spliced one-for-one at each intermediate splice, and are used during repairs to by-pass defective pairs found after the cable is in service. Generally, there is one interstitial pair per 100 pairs. A 600-pair cable, therefore, will actually contain 606 pairs. This policy is also used in PIC cable of large counts, generally 600-pairs or bigger. There are uniquely-colored PIC pairs wound into the cable that are used the same way as the ones in the pulp cable.

During routine maintenance, a tone is sent from the nearest terminal or frame, or PIC splice to determine the code. If a cable failure occurs, a team of splicers sets up as if they are installing a new cable, using talk wires, and tone is sent to identify the pairs.

Pair number 1 is in the center of the cable, along with his friends, pairs 2 - 50. As you go out towards the surface of the cable, the pair count increases. This is because in the field, the terminal furthest from the CO has the lowest numbered pair count. As the cable size decreases along a run, the outer groups of pairs drop off and feed terminals, and the center of the cable "keeps on going" so to speak.

For further reference, see BSP's in the 632-xxx-xxx series.


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Only thing I can add to what Arthur has posted is you only worried about the actual pair on the ends of the count, in the middle all you cared about was the groups were spliced group to group. This is on new splices, should a working "hot" cable get cut than all pairs had to be toned, but you knew which group to look for the tone.


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dexman Offline OP
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I think my pieces are 25 pair...but I can dig them out for a quick count.

Reading Arthur's description of how technicians worked with this cabling...I realize how lucky I am not to have to wrestle with it. Having conductors clearly marked with distinct base/stripe coloration within colored binders takes away part of the work needed to root out a specific pair during initial installation.

I am surprised to read about the elevated failure count. Is that due to the nature of the pulp insulation itself...along with the fabric sleeves that were used when conductors were joined (soldered) together?


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Installers didn't have to worry about it. They worked in the terminals where the count was broken out. Remember back then it was all binding post to the installers, not cable pairs.


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Fascinating stuff.


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You young pups missed out on the troubleshooting wet splices with a Megger. Crank until it smokes, repair burnt area, repeat as needed.


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dexman Offline OP
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Thank goodness for that!!! amen

I can only imagine what a full reel of cable...even 25 pair...must have weighed.


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Click

A BSP is always preferable to the fading memories of an old telephone man. Click the above link for the real story. Scroll down and hit "VIEW".


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dexman Offline OP
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I dug out one of the pieces of 25 pair cable. This cable was found in a riser space on the floor that Global Crossing used to lease.

The cable jacket is dark gray in color. Half of the insulators are neutral in color while the other half are striped. The stripes are very tight, but fairly clear. The insulation actually feels like cloth.

Now the old mains into the building basement were the bland colored pulp.


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