A phone cable is usually made from 0,6 mm2 copper wire. He is using a 160 mA fuse before the transformer and 125 mA fuse before the plugs. So really little current can get into the phone cable.

I have 4 pair (8 wire) telephone cable running all through the house. One pair of wire is for the telephone. Is is possible to use the three remaining pairs (6 wires) as an ethernet cable?

These days, anything with copper in it is expensive. If you doubt that, a walk into any Home Depot electrical department, where the wire is locked up tighter than Fort Knox, will prove otherwise. C… ...

Fibre-optic cable is being laid across the UK at great expense to speed up people’s internet connections, but researchers claim that the copper telephone wire already in use across the country ...