3Com V3000 ANALOG, Installation Manual

Page: 85 / 252

Installation Questions 85
What External
Devices Can Connect
to an NBX System?
The following devices can be connected to an NBX system:
■
Music-on-hold device, such as a radio, tape player, disk player, or
computer sound card, equipped with a line out (600 ohm) connection
can be connected directly into the NCP to provide audio for callers
waiting on hold.
■
Third-party Ethernet hubs and switches.
■
An ISDN (Integrated Services Digital Network) router, Frame Relay
Access Device (FRAD) router, or Voice Over IP gateway.
■
A WAN. You can access NBX systems located at branch offices
through a wide area network (WAN). Before you use the NBX system
for voice over the WAN, verify that the WAN offers adequate
bandwidth, and that the gateways can be configured to provide the
correct routing information.
■
External paging amplifier. The NBX system includes an RJ-11 jack to
connect an externally powered paging amplifier.
What Effect Does an
NBX System Have on
a LAN?
A 100 Mbps Ethernet LAN can support a fully configured, fully utilized
NBX system. That is, a 100 Mpbs LAN can support toll-quality audio with
a fully configured NBX system. If you use an Ethernet switch, verify that it
supports the 802.1P and 802.1Q specifications.
Silence Suppression and Bandwidth
Silence suppression enables you to reduce network traffic. When silence
suppression is enabled, the NBX device detects silence in the audio
stream, such as a pause in conversation, and stops sending packets. The
receiving NBX device generates white noise for the periods represented
by silence indicator packets so that the listener does not hear true silence
as if the call had been disconnected. The receiving NBX device can be
another 3Com telephone or for external calls it can be an analog line port
or a channel on an NBX Digital Line Card.
A careful listener might notice the difference between generated and
actual background noise, so silence suppression is turned off by default.
Silence Suppression results in a small compromise to audio quality. Do not
enable Silence Suppression unless you are trying to solve bandwidth
constraint issues.
You can enable or disable silence suppression for the entire system or for
individual telephones and line card ports.