serial over closed loop landline?

Hi all,

Goal: serial communication within my apartment via existing phone wiring.

Conditions: I live in the US I don't pay for phone service There's an RJ11 jack in every room

Concerns: is it possible? Are there any phone laws I might encroach on other than the gray area of using power-over-rj11? Are there extra steps with multiple serial devices communicating on the same line?

Larger goal: I'm aiming to use this for a cheap home automation system interconnect. A hub will be Ethernet enabled to be accessible outside the closed loop. Regardless of the immediate project It'd be handy for other projects.

Tips, alternate suggestions and pointers to good reference always welcome. I don't expect answers to fall into my lap, but I do appreciate at least a good push in the right direction.


Does the wiring go outside of the apartment? If it does, can you break that connection?

RJ11 is twisted pair wiring, yes? Use RS485 buffer at each location you want to talk to. Connect to a single pair of wires for half-duplex communication. Use 2 buffers and use 2 pairs for full duplex.

Can we assume you have plugged in a real telephone and checked for a dial tone? It may still be hot to the local telephone company, just waiting for you to communicate with them and restore the phone service with a new phone number. At least that happens around here.


RJ11 is twisted pair wiring, yes?

I think the RJ11 is the telephone plug/jack type. Most typical phone wire is four conductor cat3 wire which is not twisted.