66 block

A type of punch-down block designed to terminate telephone connections. The numeral 66 refers to the model number of the earliest blocks.

The precursor to the patch panel is the punch-down block, which is a panel of voice or data receptors into which twisted-pair wire is inserted, or punched down using a punch down tool, to complete a circuit. The type of punch-down block used on data networks is known as the 110 block. 110 blocks are more suitable for data connections than the older 66 block, which was used primarily for telephone connections. (The numerals 66 and 110 refer to the model numbers of the earliest blocks.) 110 blocks are still available in several different capacities. If you do come across 110 blocks in the field, be careful not to untwist twisted-pair cables more than one-half inch before inserting them into the punch-down block. Figure 4-9 shows a patch panel and Figure 4-10 shows a punch-down block.