66 block

The 66 series connecting block, introduced in the Bell System in 1962, was the first terminating device with insulation displacement connector technology.

66 E blocks are available pre-assembled with an RJ-21 female connector that accepts a quick connection to a 25-pair cable with a male end.

Typically, a 25-pair cable coming from the phone company is punched down on the left side of a split-type block in pairs.

An orange insulating cover attached to a 66 block denotes its designation as a demarcation point by the local exchange carrier.

110 block termination is almost always compliant with Category 5 (or higher) and therefore capable of supporting 100 MHz (or faster) signaling.