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DEFINITY Enterprise Communications Server Release 6
Installation and Test for Compact Modular Cabinets
555-230-128
Issue 3
May 1998
Install and Cable the Cabinets
Page 1-87Install Off-Premises Station Wiring
1
Circuit Protectors
Carbon block, or equivalent protection is required at both building entrances.
Also sneak current protection is required. Protection can be provided by a 4-type
protector or a 3-type protector plus a separate sneak current protector. The
4-type protector is equipped with a heat coil.
The 4-type protector is the preferred device. For installations not using primary
protection, 4-type protectors should always be used. When the 3-type protector
is already installed, a separate sneak current protector is required. The multi-pair
protector units and the off-premises cabling must be locally engineered.
Connectorized multi-pair protector units (female 25-pair connector) are
recommended. Table 1-14
shows the recommended protectors.
The maximum range of out-of-building analog telephones (500-, 2500-, or
7100-types) connected to an analog line circuit pack should be such that the
maximum loop resistance does not exceed 1300 Ohms.
The following voice terminals
cannot
be installed in an exposed environment:
■ 7300-type voice terminals connected to TN762 Hybrid Line circuit packs
■ Multi-button Electronic Telephone (MET) sets connected to TN735 MET
Line circuit packs
■ Analog telephones connected to TN746 Analog Line circuit packs
Refer to Table 1-1 on page 1-3
for circuit protector ordering information
(comcodes).
1. The 3-type protectors should only be used if they are already part of the
existing protection system. A sneak current protector is always required when
a 3-type primary protector is used.
Table 1-14. Analog Line Circuit Protectors
Protectors
Primary
1
Primary
(with heat coil)
Sneak Current
Protectors
1
3B1A (carbon) 4B1C (carbon) 220029 Fuse
3B1E-W (wide gap
gas tube)
4B1E-W (wide gap gas tube) SCP-1
3C1S (solid state) 4C1S (solid state)