For some applications, it is desirable to allow the completion of the transmission path associated with a bearer service prior to receiving call acceptance. In particular, the completion of the backward direction of the transmission path prior to receipt of a CONNECT message from the called user may be desirable to:
a) allow the called user to provide internally-generated tones and announcements that are sent in-band to the calling user prior to answer by the called user; or
b) avoid speech clipping on connections involving an NT2 where delays may occur in relaying the answer indication within the called user equipment.
The procedures described in this Annex are only applicable to the speech and 3.1 kHz audio bearer services.
Note - The definition of necessary mechanisms(if any) with Signalling System No. 7 to avoid any potential undesirable charging implications remains for further study.