[Asterisk-Users] detect SIP phone availability before dialing

[Paul Zimm]

Use application ChanIsAvail with the s option. This option only exists 
in CVS-HEAD version, the 1.0.x versions don't have this option.

from documentation:

If the option 's' is specified (state), will consider channel unavailable
when the channel is in use at all, even if it can take another call.


> This is a pretty popular question.  IIRC SIP phones can't tell you 
> their statuses, you need to send a call to them and determine whether 
> or not they're Busy Now...
>
> bman at host.sk wrote:
>
>> Hello,
>>
>>  I need to detect availability of SIP phone before dialing. I need to
>> know if phone is  BUSY, CHANUNAVAIL before dialing. If phone is 
>> "free", then I will dial
>> it.
>