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Chapter 4 - Installing Videoconferencing Systems
© Polycom, Inc. 83
If You Are Connecting to a PBX
❑ Some PBXs require a crossover cable.
❑ The PBX must provide the clock signal and act as the network
side for layers 1, 2, and 3.
❑ QSIG signaling (PSS1) is not supported. However, a PRI
network interface module can be connected to a PISN through a
gateway using ETSI DSS1 signaling.
Cables Used with the PRI Network Interface Module
The following cables may be used with the PRI network interface
module.
❑ Peripheral link cable: The peripheral link cable does not fit into
a standard RJ-45 network port. You can, however, use it to
connect any Polycom network interface module to the system.
❑ PBX crossover cable: An RJ-45 crossover cable may be required
when connecting the PRI network interface module to a PBX or
other third-party network access device.
❑ PRI Cable extension: You can purchase a cable adapter kit to
extend the distance between your system and the PRI network
interface module.
❑ 75 Ω coaxial adapter: The PRI E1 line termination is 120 Ω. In
some areas, however, the E1 network connection is via a 75 Ω
coaxial cable. The PRI network interface module does not
directly support this, but you can obtain passive adapter
devices from various vendors.