The 2026 Ultimate Guide to Cable Avoidance (CAT & Genny)
A CAT and Genny is the standard two-part kit for finding buried services before you dig. The CAT (Cable Avoidance Tool) listens for the signals given off by buried cables and pipes; the Genny (signal generator) applies a traceable signal to a specific service so the CAT can follow it. Used together, and used properly, they are your first defence against a cable strike.
That sounds simple. In practice, most strikes happen not because the kit failed but because the operator swept too fast, trusted Power mode in a noisy location, or skipped a calibration check. This guide pulls together what actually keeps people safe on UK sites in 2026, from the physics behind the beep to the modes you should be using and when.
What does a CAT and Genny actually detect?
A CAT detects three different things, depending on the mode you select:
- Power: the 50Hz field radiating from live mains cables. No Genny needed, but it only finds loaded cables, and it goes quiet near a perfectly balanced or unloaded supply.
- Radio: very low frequency radio signals that re-radiate along long metal services such as pipes and cable sheaths. Again passive, no Genny required.
- Genny (active) signal: a 33kHz signal you apply yourself with the Genny, either by connection, by clamp, or by induction. This is the only mode that lets you trace a specific service and the only reliable way to find unloaded cables and metallic pipes.
The honest limitation: a standard CAT finds metal and live power. It does not see empty plastic water pipes, clay drains or fibre ducts unless you trace them another way. We cover that gap in what a CAT and Genny cannot pick up.
How do you use a CAT and Genny safely on site?
The sequence that HSG47 and every decent training course drills into you:
- Check the kit. Daily function check, and confirm calibration is in date. A unit that lies to you is worse than no unit at all.
- Sweep in Power, then Radio. Walk the area in a grid, slowly, holding the CAT vertical. Mark every response.
- Apply the Genny. Connect directly to an accessible service where you can, or use a signal clamp around an isolated cable. Induction is the last resort, not the default.
- Trace and confirm depth. Follow the applied signal, then take a depth reading to inform your safe-dig method.
- Dig with care. Hand-dig trial holes; the locator narrows the risk, it does not remove it.
The single biggest technique error is sweep speed. Move the CAT like a metal detector at a slow walking pace. Rush it and a shallow cable can pass under the antenna before the unit reacts.
What does the SWING warning mean, and why does it matter?
Modern Radiodetection CATs watch how you hold and move the unit. If you swing the CAT like a pendulum, or hold it at an angle, the readings become unreliable. The SWING alert nags you to keep it vertical and steady. It is not a gimmick: poor technique is the root of most false "all clear" readings. There is a full breakdown in our gCAT4 SWING and operator technique guide.
Power, Radio or Genny: which mode finds what?
| Mode | Finds | Misses |
|---|---|---|
| Power | Live, loaded mains cables | Unloaded/balanced cables, pipes, drains |
| Radio | Long metallic pipes and cable sheaths | Short services, plastic, empty ducts |
| Genny (33kHz) | Any service you can apply a signal to, plus traced pipes via sonde | Services you cannot access or clamp |
Good practice is to use all three. Power and Radio give you the quick passive picture; the Genny lets you confirm and trace individual services. Working near 25kV rail or an EV charging hub changes the rules, because electrical noise floods Power mode; see our guide to locating in high-interference environments.
How often should a CAT and Genny be calibrated?
Annually, as a minimum, and most fleet policies and CALSafe settings enforce a 12-month interval. Calibration confirms the unit responds at the right sensitivity; drift is invisible until the day it costs you. We run an accredited CAT and Genny calibration, service and repair service, and we explain the why in why calibration matters.
Should you buy, hire or refurbish?
It depends on how often you locate:
- Hire if you need a CAT for a one-off job or a short project. Our CAT and Genny hire rates include calibrated kit, ready to use.
- Buy refurbished for the best value on a daily-use tool. A reconditioned Radiodetection CAT4 and Genny4 kit arrives calibrated with a warranty, typically at a large saving over new. The case for it is set out in refurbished vs new CAT4.
- Buy new when you need the latest data-logging and fleet management features across a large team.
Not sure which brand? Our CAT4 vs C.Scope vs Leica ULTRA comparison weighs the three names you will actually be choosing between.
Where does training fit in?
HSG47 is explicit that locating equipment must be used by competent people. The best CAT in the world is a paperweight in untrained hands. We recommend a tiered approach: manufacturer familiarisation first, then a recognised EUSR or City & Guilds course on Genny use and swing technique, and data-log analysis for supervisors. Browse the full cable avoidance range when you are ready to kit out a team.
The bottom line
Cable avoidance is a discipline, not a device. Sweep slowly, use the Genny to confirm rather than guess, keep the unit vertical, keep it in calibration, and never read silence as safety. Get those habits right and a CAT and Genny will do exactly what it is meant to: keep your spade away from a live cable.