The proper term for call collapsing is "TBCT"
 

In telephony there is a very desirable feature, that
is sometimes called "hook-flash" or blind transfer.

The above terms apply to analog calls; in ISDN PRI the basic
behavior is the same, but the terms are things like "2-B Channel
Call Transfer (TBCT)", "call deflection", "release line trunking
(RLT)". I would like to apply this channel-saving feature to
a Cisco AS-5300. There is plenty of information about the case
in which the Cisco is in user-side mode but in my case the Cisco
port is in NI network-side emulation mode. So the question is:
can the Cisco be told to short-circuit a call and leave the
requesting device (the NI user side, a Dialogic board) alone? How?

Thanks for sharing your expertise...

-Ramon F. Herrera