Greg explores troubleshooting the oldest form of communication current network administrators are likely to encounter, the Plain Old Telephone System. Discover how a buttset is used to test phone lines. Explore some common ways to test between a phone and the provider's DEMARC. Learn how inexpensive alternatives may be used in place of specialized testing tools.
- [Narrator] The plain old telephone system may seem antiquated. Let's not mince words. It is antiquated. But from time to time, I still have to troubleshoot a physical phone. Many systems still run on analog phone lines, from standard phones, fire system dialers, elevator emergency phones, ATM machines, to the trusty fax machine. These lines can be delivered either via the phone company or from live VoIP system via an analog converter.
Once they are analog signals on the copper, the troubleshooting process is the same. The process starts with a tool called a lineman's handset, or a butt set. A butt set is a hardened analog phone with test leads connected. It is hardened to absorb abuse while clipped to a tool belt, and the leads are generally wrapped in a woven material for strength. The leads terminate in clips that can be attached to a common POTS terminal block. They often have a bed of nails, which is a pad of spikes that can directly bite through the jacket of a cable.
Most modern butt sets also include the ability to directly plug into an RJ11 connectorized cable for testing. I generally begin my troubleshooting by testing the line right where the device plugs into it. Simply the connect the phone cable directly into the butt set, and test the line. If the line comes up and dials out, I know I have an issue with the device. If the butt set gets no dial tone here, I'll go straight to the DMARC, or the closest point to my connection on the provider's network.
The majority of tel code DMARCs consist of a 66 block. It's for this reason the majority of butt sets have clips that accept 66-block pins. I find that issues generally originate either with the end device or within the provider's network, which is why I test these first. Once I locate the proper pair of cable at the DMARC, I'll clip my butt set's test leads on the jacks. If I still don't get dial tone, then I've effectively pinpointed the issue as within the provider's network, and I'll contact them to repair the issue.
Before I call the provider, I'll usually pull their cable out of the DMARC in an attempt to re-terminate it, just to be sure a connection hasn't come loose or corroded. If I do get dial tone, I know that the issue is in the cable connecting the DMARC to the end device. The easiest method to troubleshoot from here is to work from the DMARC towards the end device, testing each connection in the cable until the fault is located. A standard $5 analog phone can be used in place of a butt set.
Actually, it should work just fine for occasional use. When testing at the phone, I can simply plug the existing cable into the phone. When testing at the DMARC, I can strip about 1/2 an inch of phone cable and wrap the bare wires around the leads on the tel code's DMARC. Other than this, all testing steps are the same. Though analog phones are nearly a 200-year-old technology, they can still be integral to your business and will often fall under the IT purview, so be prepared to troubleshoot.
Even if you're rusty on your OSI model knowledge, this course is invaluable if you're having trouble with your network. It offers a clear, practical troubleshooting guide to narrowing down and solving most problems related to network connectivity.
- Troubleshooting the physical layer: POTS, Ethernet, and more
- Troubleshooting the data link layer
- Troubleshooting the network layer
- Troubleshooting the transport layer
- Troubleshooting Wi-Fi
- Troubleshooting proactively