V5 Phone Cables

So I am working with my testbed and I need more cables. Can I use cables that I did not buy from vex or will that break the part because of bad wiring? Please keep in mind this will not be used at the competition.

Are you talking about the wires that connect from the brain to the motors?

Yes, I don’t have any of those and I was wandering if a phone wire would work because the connector fits

Are you sure you are talking about the ones for the brains and motors or are you talking about the one that goes from a brain to a computer.

Brain to the motor. My dad has wires that have the same connector but the internal wires are not in the same position and I am wondering if that will break the part

Well I am not sure then. I guess the only way to know is to try but personally if you really don’t need to use them I wouldn’t risk it.

Telephone cables do not use the same connector and do not have the same wiring.

DO NOT try to use them as V5 Smart Cables.

Edit: I should have realized this initially, but it was brought to my attention that such a cable may actually work. However, I still do not recommend it for the untrained user, as quality of such cables can vary significantly and the wiring configuration may not actually be what you think it is.

In theory, VEX implemented appropriate measures to protect against damage to V5 components as a result of using unsuitable cables, but I wouldn’t take my chances given V5’s historical reliability.


Thank you I could have broken my test bed

We’ve used standard RJ11 cables in the past when we ran out of vex stock and wanted to test before a new batch shipped. Worked just fine - however it probably wouldn’t be legal in a competition setting. If you do need to use something else, just make sure it’s a 4 wire cable and the connector fits in the socket, you should be fine for a while until you have access to legal vex cables again.


No “probably” about it. Checking for the “V5” marking on cables is part of the inspector’s job, on the inspection checklist: https://www.robotevents.com/season/130/document/77/download


RJ11 is a 6P4C connector and thus would not fit in a V5 Smart Port.

You likely used RJ9 (4P4C) instead, as is found on telephone handset cables. These will work if they are straight-through, but I wouldn’t be surprised if a crossover cable would break the port. And who knows what would happen if the wiring configuration was something other than those (probably, bad things).

I stand by what I said earlier. If you don’t know how to test the cables to make sure they are straight-through, just stick to the VEX cables.


Even if wired correctly, you may notice performance issues with V5 Smart Motors if they are connected to a V5 Robot Brain using off-the-shelf 4P4C telephone cables. V5 4P4C connectors and Smart Cables are rated for higher sustained current draw than most off-the-shelf telephone components.