In March 2024, I was the guy who made an $890 mistake with a multimeter on a General-Cable Cat6 run. If you've ever terminated a nice new drop, looked at your clean T568B, and used a multimeter to feel like you tested it, this story is for you.
Background: The General Cable 7136100 in the Warehouse
I work for a small low-voltage contractor. We won a 12-drop office fit-out in a building with an old phone system that still needed one extension. The owner bought a partial pallet of General Cable 7136100 boxes from a supplier clearing stock. The label said General Cable Industries Inc, and it was CMP-rated Cat6, 23 AWG, 1000 ft. That cable was not the problem.
We also had a spool in the back with a faded label that read general-cable 3310. I never looked it up before that day. I assumed it was legacy voice stuff, the kind of cable that sits in a warehouse until someone gets rid of it. That spool became useful later, but not for the reason I expected.
The Day I Trusted the Beep
The conference room drop was the fifth one I terminated that morning. I had already done the data closet and two offices. On the conference room run, I terminated the patch panel end first. At the far end, the cable was still unterminated. I stripped the jacket, twisted the blue pair together, and went back to the patch panel. The meter read 6.3 ohms. That made sense for the length. I did the same for orange, green, and brown. All four pairs beeped.
I texted my supervisor: all pairs good.
Then I terminated the wall jack. That is where I created the split pair. I did not test the completed link with the multimeter, because there wasn't a clean way to do it. I closed the jack and called it done.
Honestly, the beep was true, but the conclusion was wrong. From the outside, a continuity beep looks like proof that a cable is healthy. The reality is that a Category 6 link is about much more than copper touching copper.
What the Multimeter Couldn't See
Two days later, the client's network engineer showed up with his certification tester. He certified the data closet drops first. Then he hit my conference room run. The tester displayed a wire map failure caused by a split pair.
A split pair is exactly what a continuity test cannot catch. The DC path is still there. Every conductor is connected to the correct pin at the far end. But the pairing is wrong, which breaks the twisted-pair signal relationship. Modern networks send data over all four pairs and use frequencies up to 250 MHz for Category 6. A multimeter does not measure crosstalk, return loss, or signal echo.
He looked at my meter and said, Good. Now show me the failure the network will see. I didn't have an answer.
That one mistake cost $890. A truck roll, a re-termination of both ends, a retest, and a delay. I still kick myself. If I had told the client we would certify the drop the next morning, we would have saved the money and the embarrassment.
How to Use a Multimeter Correctly on Low-Voltage Cable
I still use a multimeter on cable jobs. The trick is knowing what it can and cannot do. Here is the checklist I follow now.
- Disconnect the cable from any switch, patch panel, or powered device before testing. A live circuit makes every reading nonsense.
- Touch the meter leads together first. If the meter does not read close to 0 ohms, your leads or your meter are the problem.
- At the far end, either have someone isolate the conductor or short the pair intentionally. If the far end is open, O.L. is not a cable failure.
- Measure from the near end. A long cable will read a few ohms, not zero. That is normal. Zero ohms between two pins of different pairs means a short.
- Test each pair in the same way, then think about whether the wire map can be wrong. If the cable has a shield, use the meter to check shield continuity to ground at the correct bonding point, not as a network test.
- Put the multimeter away after the continuity check and use a real network cable tester before you hand the drop to a client.
There is a place for an ohm meter. It is great for opens, shorts, and shield grounding. It is not a substitute for a wire map tester or a certification tester.
The 3310 Lesson
After the failed test, I looked up the old spool. The 3310 part number belonged to a legacy General Cable product line from an era when networks were much slower. The thinking that a beep is enough came from that older world. Back then, a tone generator and a multimeter could handle a lot of troubleshooting. That is not true for today's enterprise networks.
I also read the General Cable datasheet for the 7136100 again. According to the datasheet accessed in March 2025, the cable is specified for 100 ohm impedance and 250 MHz. The Category 6 rating means nothing if the termination creates a split pair. The standard says to maintain pair twists within a half inch of the connector (Source: ANSI/TIA-568.2-D, 2018). I had broken that rule.
The client never said much about the cable brand. They talked about our work. That is the part that stayed with me. The General Cable Industries Inc box was fine. The company perception problem came from my bad termination and the tool I chose to verify it.
What I Do Now
Before I terminate a General Cable Cat6 drop, I confirm the pinout, check the drawing, and untwist only as much as the jack design requires. I take a photo of the back of each jack before closing it. And I refuse to call a drop tested until I have seen a tester read PASS on the wire map.
If the only tool on site is a multimeter, I will say so. I will label the drop as continuity-only and tell the client it is not certified. It costs a little credibility in the moment, but it protects the company later.
Since then, I have maintained the team's checklist. In the past 18 months, we have caught 47 potential errors just by checking the wire map before anything else. Most of those errors were in my own terminations, which is humbling but better than lying about it.
The lesson for me was simple: the cable is only as good as the termination and the test. A $50 difference in cable quality is worth it, but paying for premium cable does not save you from checking your work with the right tool. The output, the working link, is what the client sees.
If you are about to use a multimeter on a network cable, take this from someone who has made the mistake: the beep is not the proof. The proof is a test that matches the standard the network needs.
This was accurate as of March 2024. Standards and product part numbers change, so verify current TIA references and the current Prysmian General Cable datasheet before you make assumptions.
