Electronics Need help plz

i have a circuit Diagram it's for a telephone to indicate is it in use or not .

i want to make this circuit , but my problem is :

the circuit have it's input as two terminals , 1- Ring 2- Tip

i don't know what the terminal Tip mean ,
how can i find it on the telephone board , anywone can help

http://home.maine.rr.com/randylinscott/jun99.htm

Thank you

 

The tip one is the green wire in the phone line.

http://www.homephonewiring.com/clr-code.html