Cable and pipe locator (CAT & Genny) — finding unknown buried routes before digging

The KLIC-notification guide covers the legal obligation to file an excavation notification before ground-disturbing work and to consult the drawings received. Those drawings, however, give a registered — but not always fully current or exact — picture of what is actually in the ground. This article covers the tool used to verify that in the field itself: the cable and pipe locator, commonly referred to by the brand-like term "CAT & Genny" (Cable Avoidance Tool and signal generator).

The two parts of the tool

The CAT — a handheld receiver that detects electromagnetic signals originating from, or applied to, buried metal cables and pipes.
The Genny — a portable signal generator that applies a recognisable signal to a cable or pipe (via a direct connection clamp or inductively, by placing the transmitter on the ground near the suspected route), so that cable or pipe also becomes detectable when it carries no current of its own.

Three detection modes

Power mode — detects the electromagnetic field of cables that are actually carrying current. Does not work for switched-off or unloaded cables.
Radio mode — detects broadband radio signals that naturally travel along buried metal cables and pipes, even without using a generator; useful for an initial, wide-area survey.
Genny mode — specifically detects the signal applied to a cable or pipe by the dedicated Genny signal generator.

Why a CAT without a Genny is insufficient

A CAT used only in Power and Radio mode is estimated to miss roughly half of the buried routes present: cables that carry no current, do not re-radiate a radio signal, or emit a signal too weak to be picked up reliably. Industry literature and practical guidance (such as the British HSG47, widely used as a reference in cable/pipe location practice) therefore emphasise that a CAT must always be used together with a Genny signal generator: the Genny applies an active signal to the suspected route, after which the CAT can specifically track that signal in Genny mode — even when the cable itself carries no current.

Relation to other techniques

Compared with the tone-and-probe guide: that technique requires access to at least one end of the specific conductor to be identified (to connect the tone generator) and is intended to distinguish one already-known conductor within a bundle. A CAT & Genny is intended to find the (still unknown) route of a cable or pipe in the ground, without either end necessarily being accessible.
Compared with the TDR guide: a TDR locates a fault (break, short circuit) in a cable whose route and both ends are already known. A CAT & Genny locates the route itself, before anything is known about the condition of the cable.

Practical relevance

Before digging, drilling or piling work near a suspected route, or one shown on the KLIC drawing, scanning with a CAT & Genny is the practical, on-site verification step that supplements the KLIC drawing: the drawing indicates roughly what should be there, and the detector then confirms where the route actually is in the field, including any deviation from the drawing.

Common mistakes

Using a CAT alone without a Genny — misses a significant proportion of the routes present, particularly unloaded cables and pipes that produce no radio signal.
Relying on the KLIC drawing without field verification — a drawing can be outdated or show a route that in reality has shifted several decimetres from the registered position.
Scanning the route only once instead of scanning the area from multiple directions — a single scan direction can miss a cable running parallel to that direction.
Attaching the Genny's connection clamp to a cable without first confirming it is de-energised — a direct (galvanic) Genny connection must only be made once this has been established as safe; when in doubt, use the inductive (non-contact) method instead.