Check out the video version of this post here


I had a gentlemen write me for instructions on how to use an extra Cat5e jack with a telephone. I thought the information might also be useful to others out there so I’m posting it here.

I use the T-568A wiring standard for home use. So, if you want to use a Cat5e (RJ-45) jack as a telephone interface you need to wire it as following:

CAUTION: This post illustrates how to wire up a RJ-45 jack for use with a RJ-11 connector. Please be advised, that it is wise to use voice grade RJ-11 jacks instead of RJ-45 jacks for voice or telephone systems because you run the risk of someone plugging a computer into the phone jack, which might fry or ruin the network card in the computer if the telephone rings or is plugged into a phone system. Since a RJ-45 connector won’t fit into a RJ-11 jack, you won’t ever have this risk.

Green and Red wires on standard bell systems are tip and ring for line one of service. The Black and Yellow are tip and ring for line two of service. If you have a telephone system, like a Panasonic KSU, you need both pairs since it uses the others to send status information like CO, Time, Date, Caller ID, and the likes using the phone systems proprietary protocol.

– Blue on the RJ-45 jack is equal to Green
– Blue/White on the RJ-45 is equal to Red
– Orange on the RJ-45 jack is equal to Black
– Orange/White on the RJ-45 jack is equal to Yellow

It’s that simple… you can either punch in standard 4-conductor telephone cable into the jack or you can use Cat5e and then when you connect it to your phone junction box you can connect the colors from the cat5 to the colors I have listed above.