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i2531sum.txt
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INTERNATIONAL TELECOMMUNICATION UNION
ITU-T RECOMMENDATION SUMMARY
Rec. No. : I.253.1
Title : Call waiting (CW) supplementary service
Study Group : I - Services
Version : Revised
Date of adoption : 1990
Notes :
The Call Waiting service is a supplementary service which permits a
subscriber to be notified of an incoming call (as per basic call
procedures) with an indication that no interface information channel
is available. The user then has the choice of accepting, rejecting or
ignoring the waiting call (as per basic call procedures).
The ISDN Call Waiting service allows an out-of-band notification to
subscriber B of the incoming call; this is the assumed case for the
definition.
The maximum number of calls that can be handled (e.g. active, held,
alerting, waiting) for each ISDN number on a given interface is
specified at subscription time.
Note - The situation where at least one B-channel is available may be,
for a given terminal, a situation similar to the one where all
B-channels are busy. A terminal receiving a call request and already
having an active call, may process the new incoming call in the
same way as it would have processed a call if no B-channel were
available, i.e. react positively to the incoming call request.
Moreover, when at least one B-channel is free, any compatible busy
terminal of subscriber B can react positively to an incoming call.
To order the complete text of this Recommendation, please use the
Order Form for ITU-T Recommendations. An electronic version of this
form is available on ITUDOC (Winword 2.0: UPI=ITU-5265; ASCII: UPI=ITU-2488).