Telephony Basics Pt 4

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This post was originally posted to my old blog January 25, 2012.

In previous posts, I’ve explained terminology, color coding, and how to trace cables.  Now it’s time to actually connect something.  As I showed in the first post of this series, there are two styles of punch down blocks for telephony, the 66 block, and the 110 block.  These blocks are used to connect station cabling to the trunk cabling that goes from an IDF to the MDF.

Both styles of punch block use a punch down tool to terminate the wires to the block.  Many tools have a dual blade that can be flipped depending on which style of block is in use.  To terminate a wire, you place it into the terminal and then push it down to make contact with the punch down tool.  The punch down tool fits around a 66 block terminal or into a 110 block terminal.  One side of the blade is sharp to cut the wire off flush, this is normally marked on the tool with the word cut.  Be sure to have this side oriented to cut off the loose end of the wire and not the end going to the other block.

Terminating station cables to a 66 block or 110 block is similar to jumper cables except that you have 4 or more pairs instead of one.  The color code dictates that you should lay out your pairs white/blue, white/orange, white/green, white/brown, white/slate, red/blue, etc.  Each time you put a new station cable on it’s white/blue pair would follow the previous cable’s last pair.  These pairs are punched down on a 66 block into the outermost terminal.  On a 110 block, they are terminated by placing a plastic biscuit on top and punching it down on top of the wires.  Each biscuit terminates 5 pairs of wires at a time.  While you can use a standard 110 punch down tool, it is much easier to use a tool designed to punch five pair at a time like the one pictured.  Once the biscuit is in place, the jumper wires can be terminated one pair at a time.

In the same method, larger 25-pair cables can be terminated on a 110 or 66 block.  When doing larger cables, getting a neat appearance is often tricky until you have practice.  One phone technician told me to hide the extra cable behind the block in case you ever have to re-terminate a pair so that you don’t have to re-terminate the entire cable.  Below is a good howto video from YouTube on how to do 25-pair termination to a 66 block.

How to Terminate a 66-Block to a 25 Pair Cable