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Why is it called a "66" or "110" block?

Why is it called a "66" or "110" block?

Why is it called a "66" or "110" block?

I've been punching blocks for quite a few years.  Can't remember (if I knew in the first place) why they call them "66" and "110" type blocks.  I've seen a couple of guesses at this one, but I haven't found any definite answers.  (One somebody said it was because they were invented around 1966!?  I doubt whether that's where the term came from.)  ATT created the "66" type block, I remember.  Just don't recall....

RE: Why is it called a "66" or "110" block?

All the products that WESTERN ELECTRIC manufactured always had a model or type number. The 66 series connecting block was the first IDC type connecting block in the BELL SYSTEM, introduced in 1962. It came after the 65 type. Some of the block series types are:

66A1-25, 66A2-25, 66A2-50
66B1-25, 66B4-25, 66B4-25C
66C1-16, 66C2-16, 66C2-32
66M1-25, 66M1-50
66E3-25, 66E4-25, 66E8-25

The number does mean a specific block arrangement or config in relation to the contact make up, etc.

The 110 connecting block system is an update to the original type 88 connecting block that the BELL SYSTEM introduced in the late 1970s. They wanted a more compact and reliable connecting system for phone systems.

In 1979 the type 88 was not the only connecting block system introduced to telephony, the BIX cross-connecting system from Nothern Telecom thru Cook Electric in the US and one from 3M, but I don't recall the name for it.

Hope this helps!


RE: Why is it called a "66" or "110" block?

I too have seen the 3M punchdown blocks, specifically in Telco cross connect boxes. Also don't forget about Krone blocks.

jeff moss

RE: Why is it called a "66" or "110" block?

3M is System D...

jeff moss

RE: Why is it called a "66" or "110" block?

I will never forget the look on the ATT reps face when I asked him,"I'm having problems punching down my multimode fiber cable on the 66 blocks. Any suggestions?"

Peter Buitenhek

RE: Why is it called a "66" or "110" block?

buitenhek, that's a good one.  Almost as good as one of my root-cause explanations:
The air gap on the layer 1 interface was out of spec.
(in other words, the darned thing wasn't plugged in!)

RE: Why is it called a "66" or "110" block?

66 and 110 blocks require different tools to terminate

66 blockd are the most common and you would use your '66' tool, the 110 use the 110 tool.

and,yes, there are others you may encounter also, such as the Krone and Bix types.

Good Luck,

Has been in the cabling business for about twenty years and is now the Sr PM for a cabling company located in the Los Angeles area.
Also a General Class Amatuer Radio Operator.

RE: Why is it called a "66" or "110" block?


The air gap on the layer 1 interface was out of spec.
(in other words, the darned thing wasn't plugged in!)

lol!  I will be stealing that for general use.  Uncredited.  But I pay you a star.  winky smile

RE: Why is it called a "66" or "110" block?

yep, that's definatly a usable one, another star for Lundah

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