LANCOM 1722 VoIP – LANCOM 1723 VoIP – LANCOM 1724 VoIP – LANCOM 1823 VoIP
Chapter 12: Configuring the ISDN and analog interfaces in detail
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NT mode operation always has to be set manually. With the LANCOM
1722 VoIP, if the ISDN 2 connector is set to 'Off' there may be a con-
nection to ISDN 1 in the case that the device has been set up for life-
line support by means of the DIP switches.
If an ISDN device is attached to an ISDN interface that is set to auto
and is not recognized properly, set the required protocol manually.
12.4
ISDN connection timing
To ensure trouble-free transmission, all of the components in the ISDN system
(LANCOM VoIP Router, upstream and downstream ISDN PBXs, ISDN terminal
devices and external ISDN telephone networks) have to use the same ISDN
timing. In the LANCOM VoIP Router, an ISDN interface in TE mode can take
on the timing of the ISDN line. The TE interface enables the device itself to
behave like a terminal device. In NT mode, the LANCOM VoIP Router can pass
on the on this timing over the ISDN interfaces to any connected terminal
equipment or downstream ISDN PBXs. The NT interface enables the device
itself to behave like an exchange.
Various settings are available to define the ISDN interfaces with which a
LANCOM VoIP Router receives the ISDN timing (to be passed on to the devices
at the NT interfaces).
PCM synchronization bus
: Automatically selects one of all TE or (reverse
configured) NT interfaces currently supplying a timing. If the selected
interface stops supplying a timing (e.g. because the bus is inactive), the
LANCOM VoIP Router switches to the next available interface that is sup-
plying a timing.
ISDN/S0 Bus
: This setting takes on the ISDN timing from the connection
for use by the LANCOM VoIP Router and further devices connected over
the NT interface. In this way, the timing can be switched through in par-
allel to an existing ISDN PBX at a point-to-point connection.
The selected ISDN interface has to be configured for TE mode.
The ISDN-interface settings contain two more modes which play a particular
role in this context:
DSS1 NT reverse
or
DSS1 NT point-to- point reverse
: When all ISDN
interfaces are operated in NT mode, the timing system runs "freely"
because there is no TE interface to take on the ISDN timing. If in this case
