Chapter 3. Installation
53
Planning and Installation
Off-premises connections:
Telecommunication cables that leave the facility (off-premises wiring) can be subject to lightning and / or
power surge conditions. Care must be taken that proper surge protection devices for such lines are
installed prior to connecting them to a D/I Mux III multiplexer.
Primary and Secondary Surge Protection:
Primary (first line of defense) protection must be provided at the entry point of off-premises wiring. This
is typically accomplished by connecting each line to a gas tube or carbon block protector that is in turn
connected to a substantial ground connection (one connected directly to earth ground via a heavy
conductor). A primary protection device activates during lightning or a power surge event and conducts
away nearly all of the surge energy to earth ground. When this occurs a short but intense (up to several
hundred volts) post-primary protection surge is left on the cabling to be handled by secondary protection
devices. The D/I Mux III has secondary protection built in for all interfaces that are intended for off-
premises connections. It should be emphasized that the D/I Mux III (or any similar multiplexer) without
primary surge protection cannot survive a lightning strike.
Protected Interfaces:
The following D/I Mux III interfaces are designed for off-premises (“outside plant”) connections. They are
designed to absorb the surge conditions typically encountered when connected to primary protectors.
These interfaces can also be used in on-premises (non-surge) applications if so desired.
FXO
FXS
Omni Orderwire
AC Power Supplies
OCUDP
T1 Interface Cards (30318-101 / 102 / & 103)
Non protected Interfaces:
Note that all D/I Mux III interfaces not on the above list are not designed for surge conditions and must
be connected to on-premises equipment.
Non protected interfaces such as 4-Wire Channel Units cannot withstand post-primary protection surges
such as encountered with lightning. All interfaces not on the list do not have surge protection and are
designed to be installed only in protected environments – i.e. connections to equipment within the
premises.
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