What is a toner probe?
A toner probe, also called a tone generator and probe or "fox and hound", is a two-part network tool for tracing and identifying cables. The tone generator plugs into or clips onto one end of a cable and puts an audible signal on it. The probe is held near cables at the other end, such as at a patch panel or punchdown block, and beeps loudest at the wire carrying the tone.
When techs use one
- Finding which wall jack connects to which patch panel port when the cables aren't labeled.
- Picking out one cable in a bundle in a ceiling, wall or wiring closet.
- Identifying a pair on a punchdown block for phone or data wiring.
How to trace a cable
- Connect the tone generator at the known end, for example plug it into the wall jack's RJ45 port or clip its leads to the pair.
- Turn the generator on. Many offer a steady or a warbling tone.
- At the far end, sweep the probe along the cables or patch panel ports. The tone is loudest on the matching cable.
- Label both ends once you've found it.
Disconnect the cable from switches and PoE equipment first unless the kit says it's rated for live lines.
Toner probe vs. cable tester
| Tool | What it tells you |
|---|---|
| Toner probe | Where a cable goes: which one it is in a bundle or on a panel |
| Cable tester | Whether each wire is connected and in the right order (opens, shorts, miswires) |
| Loopback plug | Whether a port or NIC can send and receive |
For the CompTIA A+ exam
Core 1 (220-1201) lists the toner probe with the other networking tools, such as the cable tester, punchdown tool and crimper. Remember the split: a toner probe finds or traces the cable, a cable tester checks its wiring.