PB-48 PATCH BAY SYSTEM
7
Customizing
Non-Normalling
As mentioned earlier, the most common customization you might want to make
is to defeat the normal links on one or more vertical pairs. For example, it may be
convenient to connect the input and output of an equalizer that is not part of your
regular set-up to the same vertical pair, as shown in Examples 1 and 3. Without
customization, the effect of doing this would be that the input and output of the
equalizer would be shorted together via the normal link (except when the equalizer
was in use, in which case the plug in the bottom, input jack would break the link.)
But some equipment may oscillate when the input and output are connected
together. This could possibly lead to damage or interfering crosstalk. There are
two ways to eliminate this problem. The easiest way is to offset the input and
output of the equalizer, or other device. Another method is to convert the vertical
pair to the non-normalled configuration, which eliminates the normal link. Both
methods are explained here.
Offsetting simply means that the devices front panel jacks are not part of the
same vertical pair, as shown in Example 4 below.
Converting a pair to non-normalled is easy to do, but due to the different con-
struction of the PB-48 and the PB-48D, the method is different for each model.
PB-48:
Remove the front cover from the patch bay by pulling it forward. If the
unit is installed in a rack, the cover may be removed without needing to dismount
the unit from the rack simply by removing only two of the four screws that secure it
in the rack. Just remove the lower left and upper right screws, and the cover can
be pulled off. To defeat the normal links on a particular module, flip it over, so that
the larger switching jack that was in the bottom front before, becomes top rear.
The circuit board remains on the left side as viewed from the front. Replace the
cover and re-install the two rack screws.
PB-48D:
If it is installed in a rack, the PB-48D must be removed to allow ac-
cess to the top surface. However, it is not necessary to disassemble the unit. The
normal linking is accomplished by means of suitcase jumper plugs. When they
are in place, the links are intact. When they are removed, a pair becomes non-
normalled. You can reach the suitcase jumpers with a pair of long-nose pliers
inserted through the rectangular openings on top of the unit. There are two for
each vertical pair, located directly behind the jacks. Both must be pulled straight
up and off to convert the pair to non-normalled.
Example 4
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