Information Technology Reference
In-Depth Information
50 is an “odd” number for 4-pair cables, so the last two positions are not needed;
only 48 positions are used. Contacts on adjacent 110-block strips may be connected
together, one position at a time, by using the 110-type patch plug. The plug stretches
vertically between two rows and connects the corresponding positions without hav-
ing to use jumper wires. The plugs correspond to the bridging clips that are used to
connect clips in adjacent columns on the 66 block.
In general, the 110 system is suitable for Category 5e (and Category 6 or AC6,
if so rated) use, as well as all lower categories. This is due to the smaller geometry
of the 110 clip and the ease of maintaining pair twist up to the very point of termi-
nation. Still, workmanship is an important consideration. Terminating wires on the
110 block is an “individual” operation, and the individual doing the termination
must be properly trained and sufficiently methodical. The station wires at the back
of the connecting block are more difficult to inspect than those on the front, so care
must be taken to maintain good-quality terminations.
The 110 connecting block is also an important component in many outlet jacks
and patch panels. It has the advantage of being extremely quick and easy to use, in
addition to providing a high-quality connection. You can probably terminate a 110
block in half the time it takes with many custom IDC types, even though you must
use a 110 punchdown tool. The comparison to conventional screw terminations is
even better. The ready availability of 110 tools makes the block ideal for outlet and
patch uses because it is likely to be in any installer's tool pouch. The quality of the
connection is an issue for these jacks, just as it is for wiring closet terminations. The
110 block allows you to easily maintain the twist right up to the point of termina-
tion, ensuring a low-crosstalk and impedance-matched connection. The major dis-
advantage to the 110 block is that it positions the contacts in a line, and thus it
might be a little wider than some of the custom IDC terminations. This restricts the
side-to-side placement of jacks somewhat on the outlet plate. Some manufacturers
of patch panels have dealt with this problem by simply placing the 110 strips in two
conventional rows, with paired wires running to each jack.
Because of the design of the wiring blocks, the 110 system is not really suited
for concurrent mounting of modular jacks, as is done with 66 blocks. However, mod-
els of patch panels with from 12 to 108 integral jacks are available. The jacks take
up horizontal spaces, reducing the wiring density. It is difficult to offer a 50-pin telco
jack mounting for the same reason. The 110 blocks tend to have cable-attached 50-
pin jacks, rather than integral ones. Any 110 block that is thus wired to a 50-pin jack
could use any of the fan-out cables that were mentioned in conjunction with the 66
blocks, but you would lose much of the simplicity of this latter method. A better
route would be to just use a patch panel with 110-type connections and either termi-
nate directly to the patch panel or wire cross-connects over to the 110 wiring block.
