Hi guys

Renovating my 1970s house at the moment and whilst removing the gib in lounge found that the Telecom copper line coming into the house was inside the wall. Basically a black copper cables twisted and connected to the lounge phone jack (presumably the first jack is the demarc point) .

I have always wondered where the the demarc was in house never having actually seen it in 8 years!!

Question: If I was install a master ADSL filter where do I do this? In the wall - where the wire come in off the street OR the first jack point? 

Thanks