Wiring – How to determine if CAT5 cable is wired for data or phone

Yes, with it being cat-5e cable, you could repurpose it as network cable by installing rj-45 jacks. Early Ethernet (10mBit & 100mBit) used two pairs (4 wires) and Gigabit typically uses all 4 pairs (all 8). Your Cat-5 link is referring to 10/100 Ethernet, so only two pairs are used. The other two pairs could carry a phone line each or another Ethernet connection (we used this on IP phones, the computer was on one half and the VOIP on the other half, figure out the color diagrams yourself for your RJ-45s on the second half). My preference is to not muck around with this as the first time you plug in a Gigabit equipped computer, you face getting full ring voltage into its RX/TX for the second set of pairs. Wire it for Gigabit using all pairs and be done with it.

In the good old days of 25 wire straight cable, daisy chain was common installation technique, with the advent of CAT-4 and above phone installations I have worked with have all been star to a central patch panel.

The yellow cables are probably Cat5e, which has 4 pairs of wires. (The beige cables are probably Cat 3, which might only have 2 pairs of wire). A single phone line only requires 1 pair, so as you can see the other pairs are just twisted off.

You definitely can reuse the cable for ethernet access, but you will lose the phone jack obviously.

Here are some things you should know about working with ethernet cabling:

• Unlike phones with are relatively low-bandwidth, ethernet cables need to be in good condition with the pairs twisted around each other properly and with properly terminated connections. The mess you show is fine for phones but will cause lots of interference with ethernet data. If you want to reuse the cabling for data you need to cut back the cable all the way to the yellow sheathing and start over with new CAT 5e terminations. The proper way to do it is to terminate all the cables at a patch panel, but you could also just crimp a regular RJ-45 on the end and connect them that way. You cannot just twist the wires together and expect to get a good signal. Also, at the other end of the cable (in the room with the jacks), you will need to do the same thing: cut back the cable to where it's clean, and start over with new RJ-45 jacks.
• Also unlike phones (and household electricity), you cannot split a cable into 2 cables just by joining the same color wires. If you have more than two devices you want to connect, you need to use an ethernet switch, which is a small appliance that will properly route the data packets between 2 or more devices.