[asterisk-users] SIP equivalent of zap "c" option

[Julian Lyndon-Smith]

At the moment, we have a feature where if someone's sip extension is
called, we also make another call to their mobile. We use the "c"
option in the zap dialstring so that the user has to press "#" after
answering to confirm the call (this prevents things like the
answermachine grabbing the call if the mobile is switched off).

We are now looking to move towards a sip provider to take all of our
ISDN calls, so instead of using zap / isdn to call the mobile, we will
be routing the call over a SIP trunk. Is there any feature of SIP that
we can use in order to duplicate this functionality (i.e. have to
press # to confirm the call)

Thanks

Julian