User guide

Busy Keys 175
Tele phon y
Tip: A busy key for virtual call numbers with destination call
number is not supported (see Virtual Call Numbers starting on
page 171). It is possible, however, to configure a busy key for a
virtual call number without destination call number. When the vir-
tual call number is called, the call is signalled by the busy key. The
call can be retrieved with the busy key.
Busy keys on the system network
Busy keys on the Forum 523/524 communications network are
realised as a subscriber model. A busy key requests busy informa-
tion to do so. The destination of a busy key keeps a dynamic list of
terminals which have to be reported when there is a status
change. This function mode is optimised for using busy keys on
the system network (see PBX Networking starting on page 152).
Please note the following points:
z Busy key information can be transferred via all connection
types of a PBX system networking: Q.SIG-ISDN, Q.SIG-IP and
SIP-Tie-Line. The Protocol extension option has to be
activated in the bundle configuration for Q.SIG-ISDN.
z Busy keys only function between Forum 500 / 5000
communications systems with the release 7 system software.
z If there are multiple lines available in a bundle for PBX system
networking, one of the lines is selected for busy-key signalling.
If this line fails, it can take a few minutes until the dynamic
subscriber list is updated.
Note: The “call number busy” busy-key function is the only one
supported for PBX system networking. The “device busy” busy-
key function requires device ID transmission. This is not sup-
ported by PBX system networking.