B-14
Operator's Manual
Oper
ati
o
n
Your PBX supports ISDN feature completion of calls to busy subscriber (CCBS).
Starting an internal callback on busy:
If you allow call waiting on your telephone (See Chapter Call Waiting Permission on
page I-44 in the Installation and Configuration Manual), you can make a phone call at your
leisure even though you are expecting an important external call. In this case, the calling
party hears the ringing tone even though you are currently carrying on another conversation.
For your part, you hear the call waiting signal. This is a signal to you that somebody else is
trying to get in touch with you. You now have the option of rejecting the call waiting party –
who then hears the engaged tone – or you can accept the call; in this case the previous call-
ing party waits in the background. Call waiting should not be allowed with fax machines and
modems, since the call waiting signal disturbs their data transfers.
1. 17. 2
Starting external callback (CCBS)
b
f
0
r
f
2
f
a
Internal dial
tone
Access
digit
External calling
number
Engaged
tone
Acknowledgement
tone
씮
c
b
g
As soon as the called party
replaces the handset after this call
Lift the handset – the system calls
the external subscriber
Call
h
No acknowledgement tone
씮
the exchange refused the desired callback.
Before punching in the suffix digit,
2
please wait three seconds.
The external subscriber must have the appropriate technical capability to be able to carry
out a callback.
With some network providers, callback to an external subscriber with a PTP connection is
not possible.
The exchange may trigger the callback before the external subscriber has replaced the
handset, due to the fact that only one of the B channels of his or her ISDN connection is
available.
An external callback on no response is not possible.
A callback is stored in the exchange for up to 45 minutes. If the subscriber has not com-
pleted his or her call within this time, the system clears the callback automatically.
In the case of a callback, you are called for up to 15 seconds. If you do not lift the handset,
the system clears the callback.
The external subscriber's telephone does not ring until you have accepted the callback
by lifting your handset.
1. 18
Call Waiting (Second Call Waiting When Your Telephone is Busy)
h
Call waiting is triggered only by external calls.
