Lets clear some things first. Is your internet working? If its not working then that engineer has to come back with line testing tools and make sure the filter is connected the it should. lt can be line noise which can only be fixed by telone themselves.
If the internet is working, l assume that its a two step connection:
1. there is a telephone line coming from your wall or from out connected to a small little white rectangle box which is called a filter or line splitter. On that little thing there ar two holes, one connecting to your phone, another connecting to to the back of the router they gave you.
This little box thing is the one which logically divides your telephone line into virtual frequencies or lines that separate your phone calls from data internet services. If that box thing is fault or wrongly connected, your internet is bound to fail.
2. The router has connection to both the little box and your computer. The connection to the little box connect your router to telone internet. The connection to the back of your computer provides internet to you computer.
Now l assume you want to use your Asus wireless router to give internet access to your phone, laptop etc.
Am l correct on my assessment?
