66E3-25 Connecting Block

The 66E3 blocks are basically wall jacks for 1A2 phone sets, making it easy to connect a 1A2 extension in an unobtrusive way. It is basically a wall mount miniature punch block and amphenol all in one, with a plastic cover cosmetically appropriate for an office environment.

A bare 25 pair cable from the KSU can come through the back of the block mounted to the wall, the strands can be punched down in the usual 66 block fashion, and allows for custom wiring/strapping. The phone set's station cable is connected to the amphenol inside the block, and a decorative plastic cover mounts over it, making for a clean wall installation as shown here:

photo courtesy of Scott Bonk. Used with permission.

The block's cover can be painted to match the wall color, allowing for it to be less conspicuous.

No special equipment needed other than a punch tool, and allows for custom wiring arrangements at each block. Another cable can be punched down on the second rows of the block to optionally extend to other extensions, making it a possible point in a chain, instead of just a termination point.

Quoting BSP 461-604-103: "The 66E3-25 and 66E4-25 connecting blocks each consist of fifty 2-terminal connectors inserted in a molded plastic block and factory-wired to a 50-contact connector."

These 25 pair connection blocks are typically mounted to the wall at the same height as AC recepticles. The block can be used as a termination point for a single 1A2 phone set, or it can be one block in a chain of extensions, allowing phones to all be "bridged" together electrically.

The punch block provides a termination point for a cut 25 pair cable near where a phone set will be located, the cable typically fished through the walls from a KSU.

Wiring

The 50 conductors from the 25 pair cable are broken out into color groups (shown in light gray at the left of each horizontal row), and the individual conductors connected as shown by their colors (above each connection point) or their amphenol pin numbers (below each connection point in parens):

This diagram can be used to help wire up the block easily by just matching the wire colors to the punch block positions.

There are two rows of pins for each color group. By convention, the lower rows (row #2,4,6,8,10 in the above diagram) are inputs to the block (typically from the KSU, or a previous 66E3 block in a chain), and the upper rows (row #1,3,5,7,9 in the above) are for optional "outputs" to other extensions, such when bridging other extensions in a chain on a single cable.

If the block is a simple termination point for only one extension, then only one cable comes into the block and its conductors punched down on the bottom row of pins as shown here:

If the block is in the middle of a bridged chain, you would punch the second cable that runs out to the next extension in the chain on the top row of pins, as shown in blue in the following diagram:

In the case of bridging (or a "chain"), two 25 pair cables enter from the back of the block; one from the KSU and is the "source" from the central office, and the other runs off to the next extension in the chain, usually another 66E3 block, as shown here: