Is it safe to join telephone cables

[XPC465]

Hello to all you good forum members again.
I wonder if someone with telephone knowledge can answer my query.
I intend fitting a telephone extension, in my bungalow, with proper BT cable. This will run nearly the full length of my bungalow, but in the loft.
I have about 20feet of proper BT telephone extension cable, which by itself will NOT be long enough. My query is, if I purchased another length of the same cable, would it be possible for me, to solder each wire together, individually, then tape them individually, so that the cable would still function correctly, or would the joining of the cables cause problems when fitting the extension.
Thanks for any assistance on this matter.

[ericmark]

In the main for telephone it does not really matter what cable is used or how far but when broad band is used having cable of the correct impedance becomes important.

With any AC current there are losses and there is a huge amount of literature on transmission lines and how they need to be correctly terminated. Very long cables could be a problem but unlikely.