[Asterisk-Users] Detecting if a call is active on chan_sip before trying INVITE? (was Sip question - allow only 1 incoming call to sip phone)

[Roy Sigurd Karlsbakk]

> Disable the call waiting feature in the phone, so it will signal "486 
> - Busy here" to additionally incoming calls.

Is it possible to test if a call to SIP/xxx is in place before dialling 
out? This could help a lot to centralize administation of whether or 
not to use call waiting instead of configuring the ATAs.

roy