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EXPOSED PORT PROTECTION
EXPOSED PORT PROTECTION
Requirements
All port packs and terminals require unique protection and grounding arrangements as defined in
the checklists (
AT&T System 75 Electrical Protection, Grounding, and Exposure Checklist
,
555-200-120 and
AT&T System 85 Electrical Protection, Grounding, and Exposure Checklist
,
555-103-120). These arrangements provide an adequate barrier to the potentially damaging vol-
tages and currents inherent in lightning and power surges present in exposed applications.
Moreover, the National Electrical Code requires that an approved protector be provided on all
exposed circuits.
Exposed Ports And Terminals Defined
Ports and terminals that utilize facilities that are subject to disturbances from lightning, ground
potential rises (GPR), or possible contact or induction from electrical power sources or circuits in
excess of 300 volts (RMS) to ground are classified as exposed. Any ports or terminals served by
such exposed facilities are classified as exposed and require protection at both the port and ter-
minal ends. The checklists contain flowcharts that are beneficial in determining exposure status
and tables to determine the type of protector required.
Out-of-Building Campus Stations
An out-of-building campus station is a telephone or voice terminal that is not physically located in
the same building as the equipment room, but is located on the same property. Both analog tele-
phones and digital voice terminals can be used as out-of-building stations
Carbon block, or equivalent, protection is required at both building entrances for analog out-of-
building stations. Sneak current protection is also required. Protection can be provided by a
4-type protector or a 3-type protector plus a separate sneak current protector. The 4-type protec-
tor is equipped with a heat coil for sneak current protection. The 4-type primary protector is the
preferred device.
Protection is required at both entrances for digital out-of-building voice terminals. There are two
different types of protectors that can be used to protect digital voice terminals and digital line cir-
cuit packs in an out-of-building environment: the 4C3S-75 Enhanced Protector and the ITW Linx
Enhanced Protector.
Note: The 4C3S-75 Enhanced Protector may only be used on Vintage 14 or newer TN754
Circuit Packs. The 4C3S-75 can be used on all vintages of the TN754B Circuit
Pack. The ITW Linx Enhanced Protector may be used on all Vintages of the TN754
and TN754B Circuit Packs.
The 4C3S-75 Enhanced Protector is equipped with a heat coil for sneak current protection and
the ITW Linx Enhanced Protector is equipped with replaceable fuses for sneak current protection.
The maximum range for out-of-building voice terminals is 3,400 feet when using 24 AWG wire
2-21