How can I balance incoming sip calls in differents ata?


I have an Asterisk running with one sip channel configured as the origin of all my incomig calls. I have too various SIP channels configured in ATA Sipura 3000 devices and I want that incoming calls through out by ATA devices. I configured this, but I want to balance the incoming calls to don’t try to call throught a busy line. It is possible to do that with Asterisk?

Now, with my configuration, when an incoming call arrives asterisk tries to put the call to the sip ata channel one by one, and I looking for a better solution.