2 master sockets

[Isitme]

It looks like the extension is connected direct to the AB terminals on the backplate. This means it is the same as putting it through a joint block. Best not use it, or if you want to use a phone make sure you use a filter.

The one thing I am not too great with is SNR and Attenuation levels, I always assumed that higher is better?

In the case of attenuation the lower the figure the better as it means you are close to the cabinet so have a shorter copper line. With noise margin, provided you have the correct speed, the noise margin does not matter much. If it is high it means your line is capable of more speed. If it is low, below 3or6 db, it means your line may struggle to maintain the connection at the speed you have.

[seawright]

Keeping it simple, lower attenuation levels are best. A high noise margin means that your line is capable of higher speed but it is currently capped by the broadband produce you subscribe to, hence the remark in my previous post about a free upgrade.