What a CAT and Genny Is, and How It Works

A "CAT and Genny" is two tools that work as a pair to find buried cables and pipes: the CAT detects, the Genny transmits. This explains what each one does, the modes the detector runs in, and — the part that keeps you safe — what each mode finds and what it misses. For why and when you scan, see the cable avoidance guide.

A brand-neutral overview of safe CAT and Genny use and the detector modes. Source: Paragon Training (a UK safety-training provider — not a kit seller). A useful primer, but as the video itself stresses, hands-on training is what makes someone competent to survey.

The CAT — the Detector

CAT stands for Cable Avoidance Tool. It's the handheld detector: it picks up electromagnetic signals radiating from buried metallic services and turns them into an audible and visual response, getting louder as you pass over a line. That's how you find a service and trace its route across the ground.

The key thing to understand is that a CAT responds to signals, not to metal — it isn't a metal detector. It hears the electromagnetic field around a live cable, a radio signal re-radiated by a long metallic pipe, or a signal that's been deliberately applied. No signal, no response — which is exactly why the second tool exists.

The Genny — the Signal Generator

The Genny is the signal generator. It applies a distinctive, traceable signal to a specific pipe or cable so the CAT can pick out that line in particular. It does this either by direct connection — clipping onto an accessible point of the service, like a meter, a street-lighting column or a hydrant — or by induction, where the generator sits on the ground above a buried line and induces a signal into it. Apply the signal with the Genny, switch the CAT to Genny mode, and you can follow that service even when it wasn't radiating anything on its own.

The Modes — and What Each One Misses

Most CATs run three modes, and many add a fourth. Brand names differ — Radiodetection, C-Scope, Leica and others — but the modes behave much the same:

• Power (P) — detects signals from loaded power cables. Misses: an unloaded or disconnected cable, which can sit silent.
• Radio (R) — detects VLF radio signals re-radiated by long metallic services. Misses: services where no radio signal is present — it isn't always there to find.
• Genny (G) — detects the signal the generator has applied. Misses: anything you haven't applied a signal to (and you can't easily apply one to plastic).
• Avoidance / All-scan (A) — listens for all signals at once; used at the start or end of a sweep as a catch-all. Useful, but not a substitute for working through the individual modes.

The pattern across all of them: each mode finds a particular kind of signal, and a service that isn't producing that signal stays invisible. That's not a fault — it's the nature of the method, and it's why a survey uses every mode, uses the Genny, and is still backed up by safe digging.

Why You Need the Genny

If you only ever used the CAT in its passive modes, you'd find loaded power cables and whatever radio signals happened to be present — and you'd miss the rest. The Genny closes that gap by letting you put a known signal onto a known service and trace it deliberately. Survey guidance is consistent on this: complete the survey using the Genny before you commit to breaking ground, because passive modes alone leave services undetected.

Even then, some services can't be traced this way — most importantly plastic and rubber pipes, which carry no signal unless one can be induced. So the honest summary is: a CAT and Genny is the right first tool for finding buried services, it's far better than guessing, and it still doesn't find everything. Next, see how this fits a real job in scanning a marquee site before you stake.

Adding Cable Avoidance to the Range

We're bringing a CAT and Genny into the Hogan range so the crews driving our stakes can scan the ground from a single supplier. If you'd like to know more, get in touch.

Email: hoganuk [at] hoganstakes.co.uk
Contact form: hoganstakes.co.uk/contact

Safety note — this is an overview, not training. This explains how the equipment works; it is not a substitute for competent, trained use of a cable locator (HSE HSG47). Safe cable avoidance depends on survey technique and judgement, not just on owning the tool.

Background drawn from HSE HSG47 and publicly available CAT & Genny training material (Paragon, Sygma Solutions, Proper DIY). Used as reference; adapted for UK practice.