Frequently Asked Questions
235
What are some of the causes for problems when sending and/or receiving faxes?
In frequent cases, the reason may be found in a problem with the ISDN-L1 reference
clock distribution. The L1 clock is delivered from the network provider. An unclean L1
clock distribution and the introduced signalling jitter is overheard by the human ear.
Nevertheless, data and fax transmissions may be disturbed by the jitter. Please check,
which ISDN lines will deliver the L1 clock. Details can be found under L1 Clock starting
on page 159.
The fax data transfer possibly is routed via a compressing VoIP connection. Please
verify, if the a/b port is configured with the “Fax” setting. For the VoIP connection,
select a VoIP profile which includes the non-compressing G.711 codec.
PBX Networking
Why is it not possible to answer calls from another communications system via
the missed calls list?
You get a call e.g. via a direct Q.SIG connection. Which line seizure codes you will need
to dial for the callback is not included automatically in the information transferred
with Q.SIG. Therefore, you need to setup the callback in the bundle configuration. Call
up the Telephony: Trunks: Trunk group page. Change the desired Q.SIG bundle and
enter the line seizure code for the callback in the Prefix for source phone number at
incoming internal input field.
Why is it not possible to reach a communications system indirectly via another
communications system?
You have interconnected e.g. three communications system with two direct Q.SIG
connections. While configuring the routes, you applied the default “Business”
selection for the Type setting. Call-switching for internal calls is possible for the in-
between communications system for internal routes only. Change the Type setting for
all affected routes to “Internal”.
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