Sip Channel State

Hai ,
In dial plan,how to get to know the status of sip channel . I want to check the status of SIP channel( SIP/500 ) before the Dial application . I found DEVICE_STATE function , but it is available in 1.6 . Is there any function in asterisk 1.4.33
I am using asterisk 1.4.33 version .

The B side SIP channel doesn’t exist before the Dial application is called. The A side’s state is determined by your specific dialplan. Did you mean something else?

Have a look at the DEVICE_STATE, CHANNEL, SIPPEER and SIPCHANINFO functions. I think the last one may be deprecated.

More generally, run “core show functions” from the CLI and look for likely ones. Then run “core show function xxxxxx” on those functions.

Thanks for the reply .
My senora is , I want to check the agent is free or not using the Agent Extension(SIP/501 ) . If the agent is free , then i should not Dial . I tried DEVICE_STATE function . but is not avaiable in my asterisk version .