Ring Detection / Can any one send me the NVLineDetect code

I am using Asterisk12.2.0.

I need to detect the ringtone to know whether an outgoing call has been answered. I searched and got that NVLineDetect can do this job.

But unfortunately, I can not find the NVLineDetect code on the net. I am wandering if anyonecan send me a copy of NVLineDetect code.

I will appriciate your kind help very much!

Your sincerely!

Zhen XIU