Data and Telephone on a Single Cat5e Cable

I fielded a tech call last week from an installer who needed to have both a telephone and data jack on a single wallplate, but only had  a single Cat5e cable available. “No problem,” I said. “As long as 1000BaseT (1000 MBps or 1 GBps) is not required at that data location, you can use two of the Cat5e pairs for data, and the other two pairs for telephone.”

The physical layer  of 10/100BaseT (10/100 MBps) networks use only two of the four pairs. 1000BaseT requires all four pairs. Which pairs do you use in this case?  With regards to T568A wiring, you use pair 2 for Receive Data,  pins 3 and 6, and pair 3 for Transmit Data, pins 1 and 2.  See the diagram.   Though it’s not recommended to “split” the pairs of a Cat5e cable, you gotta do what you gotta do if all you have is that single cable.  The leftover pairs 1 and 4 could then be used for telephone.  As a standard practice, keep the integrity of the pairs by keeping the twists tight right up to the punch-down point.

Speaking of RJ45 connectors, have you seen these EZ-type of connectors? They are from Platinum Tools, and the EZ RJ45 connector allows you to push the twisted pairs into the connector, and have a portion of the wires extend past the face of the connector. You can then ”EZ-ly” verify that the color scheme matches T568A, and you can pull on the wires tight to get the twists as close as possible into the body of the connector.  Use the crimping tool and then cut off the wires from the connector.

EZ connectors are available for Cat6 telephone connectors, too.