Voice Ports; Backup Pots Connection (Rj-11 Line Connector) - Cisco uBR924 Installation Manual

Chapter 1 Product Overview
For network performance reasons Cisco recommends a maximum limit of 16 CPE devices
Note
in either bridging or routing mode. The service provider may also set a different limit by
changing the MAX CPE parameter in the DOCSIS configuration file—the default MAX
CPE value is one CPE device, which applies in both bridging and routing modes.

Voice Ports

As Figure 1-6 shows, the Cisco uBR924 router contains two FXS VoIP ports that are labelled V1+V2
and V2 at the rear of the unit. These ports can be connected directly to analog telephones or fax devices,
or to adapters that allow multiple analog telephones or fax devices to be connected to each of the two
VoIP telephone lines.
The V1+V2 port on the Cisco uBR924 is a 4-wire port, with the second telco pair wired in parallel with
V2. A two-line analog telephone can be connected, therefore, to the V1+V2 port. In this configuration,
devices plugged into the V2 port act as extensions to the line 2 telephone.
Do not connect the V1+V2 and V2 ports to telephone wires that exit the building without
Caution
appropriate agency-approved protection devices. This is a safety hazard.
Between 5 and 10 analog telephone devices can be connected to each of the 2 VoIP telephone lines,
provided each telephone line does not exceed its Ringer Equivalence Number (REN). In most areas, the
sum of the RENs of all devices on any one line should not exceed five. If too many devices are attached,
they may not ring properly.
Only one voice call—telephone or fax—per VoIP line is active at a time. The actual
Note
number of voice devices supported depends on the services purchased from the service
provider and on the Cisco IOS image that is running on the router.
Typical length of telephone wire is 3,000 feet (or more) of 26 gauge. The wiring in the average small
business usually does not exceed this limit, so the Cisco uBR924 router can support the number of
telephones or fax devices typically found in small businesses.

Backup POTS Connection (RJ-11 Line Connector)

The Cisco uBR924 router provides an RJ-11 cutover port that connects to a standard analog telephone
wall jack. In the event of a building power failure or other Cisco uBR924 power problem, this port
connects the VoIP ports to the backup PSTN line. If the Cisco uBR924 router loses power while VoIP
calls are in progress, the subscriber can re-establish one of the two connections by dialing out over the
PSTN.
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Cisco uBR924 Router Hardware Installation Guide
Features
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