Information Technology Reference
In-Depth Information
The 110 system also offers a number of clip-on adapters that connect adapter
jacks, cables, and other devices to the front of a 110C connecting block. Few, if any,
of these are really practical for the orderly, structured wiring approach we have
advocated for LAN wiring. In most cases, these adapters cannot be used for higher
categories of operations, such as Category 5e/6. However, they are handy for test-
ing, as you can easily adapt cable scanners and other testers to the block wiring.
The design of 110 wiring blocks makes direct wall mounting, without a back-
board, somewhat easier. This is due to the multiple rows of index strips that are an
integral part of the wiring block. A 300-pair block could be mounted all at once,
whereas the 66 block equivalent would require mounting at least six separate
blocks. That would require a lot of wall anchors to mount to a hollow wall.
However, we are not at all advocating abandoning the backboard. It is a part of the
recommended standards for TRs, and is a very convenient way to provide a struc-
turally sound mounting for many wiring components.
Relay rack and equipment mounting options are also available for 110 system
wiring blocks. These methods are very good for large installations with the need for
significant wire management.
The wiring color codes were covered in detail in the earlier section on 66
blocks and are identical for the 110-block system. The length of the horizontal
index strips, on which the connecting blocks mount, are the same 50 wiring posi-
tions as the 66 block. However, the 110 system has the added advantage of placing
color coding on some of the 110 components, to make placing the wires much eas-
ier. When you get to a very large installation, this can be quite an advantage, as it
can also be used to visually inspect the terminations for correct routing.
Type 66M Connecting Blocks
The original workhorse of telecommunications termination is the type 66 connect-
ing block, shown in Fig. 7.4. This style of termination block has been around for
decades, and its use in the telephone industry is pervasive.
There are several types of 66 blocks, but the most common is the 66M1-
50. This block has 50 horizontal rows of wire termination contacts, with four
bifurcated contact prongs in each row. ( Bifurcated means the contact is split in
two, so that the wire can be held in place by the bifurcated fingers of the con-
tact.) Each contact unit is called a clip , and the contact clips in this style of
block each have two prongs, stamped from the same piece of metal. The four
contact prongs in each row are paired 1-2, 3-4, with each pair of contacts elec-
trically and mechanically connected. Figure 7.5 shows a cutaway view of one
contact row. Some varieties of the 66M block have four common contacts in
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