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4001231 Rev A WebSTAR Model DPX213 VoIP DOCSIS Cable Modem User's Guide 31
Telephone Requirements
Introduction
This section provides hardware and software requirements for utilizing your cable
modem for telephone service.
Number of Telephone Devices
The RJ-11 telephone-style connectors on the cable modem can each provide
telephone service to multiple telephones, fax machines, and analog modems. The
maximum number of telephone devices connected to each RJ-11 port is limited by
the total Ringing Load of the telephone devices that are connected. Many telephone
devices are marked with a Ringer Equivalent Number (REN). Each telephone port
on the cable modem can support up to a 5 REN load. The sum of the REN load on all
of the telephone devices attached to each port must not exceed 5 REN.
Telephone Device Types
You can use telephone devices that are not labeled with a REN number, but the
maximum number of attached telephone devices cannot be accurately calculated.
With telephone devices that are not labeled, each device should be connected and
the ring signal should be tested before adding additional devices. If too many
telephone devices are attached and the ring signal can no longer be heard, telephone
devices should be removed until the ring signal works properly.
Telephones, fax machines, and other telephone devices should use the center 2 pins
of the RJ-11 connectors to connect to the cable modem telephone ports. Some
telephones use other pins on the RJ-11 connectors and require adapters in order to
work.
Dialing Requirements
All of your telephones must support Dual Tone Multi-Frequency (DTMF) touch-tone
dialing.
Important: Pulse dialing is not supported.
Telephone Wiring Requirements
The cable modem is designed to support interior telephone wiring. The maximum
distance from the unit to the most distant telephone device must not exceed 1000 feet
(300 meters). Use 26-gauge twisted-pair, or larger, telephone wiring.
Important: Connection to an existing or a new permanently installed home
telephone wiring network must be done by a qualified installer.