LANCOM VoIP Routers: PBX Functionalities
Chapter 6: Extended functions
43
EN
6 Extended functions
This section introduces extended functions that demand a more in-depth
understanding of the PBX in the LANCOM Business-VoIP-Router and of PBXs
in general. Please refer to the LCOS reference manual where necessary.
6.1
Setting up call forwarding in the telephone exchange
Within ISDN networks, terminal devices (telephones) use a set of control
sequences—the so-called ISDN facilities—for communications with the
exchange. These facilities allow, for example, call transfers to be set up at the
telephone exchange. For example, if the exchange receives the sequence
*21*0123456789#
, all calls intended for the telephone number or MSN that
issued the sequence will be forwarded to the telephone number
"0123456789". Call forwarding at the exchange prevents ISDN channels from
being blocked, unlike the case when call forwarding is handled by the
telephone itself.
To provide a local telephone infrastructure with the functions of a PBX, the
LANCOM Business-VoIP-Router must be able to process the ISDN-network
control characters, and consequently these characters can no longer be
forwarded to the exchange. The LANCOM Business-VoIP-Router itself
becomes the exchange for any telephones connected to it and it manages all
incoming and outgoing telephone calls. In case of call forwarding the
sequence
*21*0123456789#
sent to the LANCOM Business-VoIP-Router
instructs it to forward all incoming calls to the number "0123456789". The
ISDN exchange does not have any information about this call forwarding.
The disadvantage of this variant is that call forwarding blocks two ISDN
channels in the LANCOM Business-VoIP-Router, even though none of the
local users is making a call.
Local
External
ISDN
ISDN
LANCOM
Business-