I have european telephone cables running through my walls to each room, without any connection/socket. Well... we really do not need any hard line telephone connection and I am into DIY projects, so I want to make use of these cables. I thought I could use these lines to deliver DC power to my Raspberry Pis and Arduinos around the house (sensors and stuff). But I really do not know how much voltage and current I can allow through these cables. One other possibility is to use them for speakers around the house (music or communication). Again speakers will need audio and power and I want to avoid switching cables as much as possible. PoE is an option I am considering, which is known/established but expansive with switches/injectors and splitters with 3+ devices.
I was wondering, if I can use existing phone cables for power (from a main AC to DC (48V?) converter, NOT from phone company of course)? Are there any standards for cable resistance/thickness and allowed potential and current?