In fact there is a quasi standard coping with a number of problems with such a 1-wire-network. It uses all 8 connections of the RJ-45 connector of a CAT5 cable including a secondary data line and a 12V power line.
1-Wire CAT5-cable use (colours by EIA/TIA-568A):
| Pin | Colour | Definition |
| - | - | - |
| 1 | white/green | 5V power ground |
| 2 | green | +5V (max. 50mA) |
| 3 | white/orange | secondary signal ground |
| 4 | blue | primary data line |
| 5 | white/blue | primary signal ground |
| 6 | orange | secondary data line |
| 7 | white/Brown | 12V unregulated supply (max. 200mA) |
| 8 | brown | 12V power ground |
BEWARE: not all manufacturers of 1-wire-sensors with RJ45 connector follow this quasi standard. Always consult the documentation of the sensor or you may destroy part of your network. By Maxim only part of these definitions are defined.
You should use an own power regulator in a sensor using the 12V line, because you get a voltage drop over the cable depending on cable length and used current (AWG 26=146Ω/1000m). In 100m distance with using 200mA of current the drop will already be 0,2A*0.146Ω/m*100m = 2.92V; so the 5V line will be reduced to 2.08V and the whole system won't work any longer. No more than about 300mA can be used on these lines!
Because on a RJ-12 connector (6P6C) the middle 6 pins are used, you will get Pin 2 to 7 of this definition, but remind that for connections over several meters there should be a sheilding. For RJ-14 (6P4C) you get pins 3 to 6 and will loose the power lines but may misuse the secondary data lines for power.