What is a CAT & Genny?
A CAT detects suitable electromagnetic signals associated with buried services. A Genny applies a signal that a compatible locator can trace. Together, they help a trained operator investigate underground cables and pipes.
Detectability depends on the service, the signal, the equipment and the site. This guide explains the modes, plastic-pipe limitations and calibration checks that help avoid false confidence before excavation.
What does each mode detect?
Select a mode to see the signal principle. The full comparison below stays available for reference.
Power mode
Detects some signals originating from electricity networks. A live or energised cable does not always produce a detectable signal, and a power signal can appear on another conductive service.
| Mode | Signal and limitation |
|---|---|
| Power | Detects certain power-frequency signals on buried conductors. A cable can carry no detectable signal, and the reading does not prove that the detected object is an electrical cable. |
| Radio | Detects radio signals carried and re-radiated by suitable conductors. Those signals may be weak or absent. |
| Genny | Detects a compatible signal deliberately applied by the generator. The application method matters, and the signal can transfer to neighbouring services. |
| Avoidance / Auto | Combines the signals supported by that model. Radiodetection C.A.T4 Avoidance Mode covers Power, Radio and Genny signals; another manufacturer’s combined mode may behave differently. |
Use the exact model’s instructions. Mode names alone do not establish which frequencies, warning features or depth functions are available. Our CAT4 and C.Scope comparison looks more closely at equipment differences.
The CAT responds to the signal, not a reliable visual identity of the buried object. Several nearby conductors can complicate the reading, so tracing and interpretation remain essential.
How does the Genny help?
Active locating creates a signal to investigate rather than relying solely on signals already present.
| Method | What it does |
|---|---|
| Direct connection | Uses suitable leads and a permitted accessible connection to apply a signal to a conductive service. This requires the correct procedure and competence; do not connect to live electrical conductors. |
| Signal clamp | A compatible clamp couples the generator’s signal onto an accessible cable or pipe where that method is appropriate. |
| Induction | The generator broadcasts a signal that can couple onto nearby conductors. It can energise more than the intended service, so the operator must account for unwanted coupling and direct pickup. |
| Sonde or traceable accessory | A suitable accessory introduced into an accessible pipe or duct provides a signal to locate or trace. Compatibility, access and the specific equipment’s instructions matter. |
A Genny is valuable because passive Power and Radio signals are not reliably present on every service. It still cannot make all materials detectable, distinguish every adjacent service, or compensate for an unsuitable search method.
This overview deliberately leaves connection methods, working distances and scanning sequences to practical training and the manufacturer’s operating instructions. A generic internet diagram should not be used as a field procedure.
Can a CAT find plastic water pipes?
A conventional electromagnetic CAT normally cannot detect the plastic pipe itself. It needs a detectable feature.
A pipe with a tracer wire
A suitable metallic tracer wire laid with a non-metallic pipe may carry a locating signal. The operator is following the wire, so its continuity and relationship to the pipe need consideration. A broken or incorrectly routed tracer is a limitation.
An accessible pipe or duct
A compatible sonde or traceable rod may help when it can be introduced safely into the service. A sonde identifies its own position; a traceable rod can support route tracing according to the accessory’s design.
No usable tracer or access
Changing to Genny mode does not make untraceable plastic visible. The job may need another suitable locating method and a revised investigation and excavation approach. Use the site assessment and competent advice to decide what is appropriate.
Where locating fits into safe digging.
HSE’s HSG47 identifies three connected elements. The locator contributes to one part of that system.
Plan the work
Obtain available service information, assess the work area and investigate site clues. Plans can be incomplete or inaccurate.
Locate and identify
Use competent operators, suitable equipment and the required modes. Trace and mark findings, and investigate uncertainty.
Excavate safely
Use the safe excavation approach for the site and services. Confirm positions as work progresses and account for changes in route or depth.
Before relying on the equipment, complete its prescribed pre-use and functional checks. Look for damage to the housing, connectors and accessories, battery or display problems and any warning that requires attention.
A reading is a piece of evidence within the site assessment. A depth estimate is not permission to use a mechanical excavator above a conductor. Continue checking as the job progresses rather than treating the first sweep as a permanent clearance certificate.
If the equipment’s behaviour or the service route is uncertain, stop the affected activity and resolve that uncertainty through the site’s safe system of work.
What does calibration tell you?
It checks defined equipment performance at a point in time. It does not certify that a site is free of buried services.
Calibration compares performance with suitable reference signals and tolerances. Associated functional checks can identify faults that call for adjustment, repair or removal from use. The scope differs between makes and models.
A sensible enquiry identifies both the receiver and generator. Ask which modes, outputs, accessories and functions are included, how any failed checks are reported, and whether repairs need separate agreement.
PUWER requires work equipment to be maintained in an efficient state, efficient working order and good repair. HSG47 advises regular checks and calibration of detecting devices. Neither provides one universal twelve-month calibration period for every CAT and Genny.
How often should it be calibrated?
Follow the manufacturer’s instructions and your maintenance programme, taking account of use and condition. Annual calibration is common; damage, water ingress, a failed check or a repair can require earlier assessment. Radiodetection instructs users not to trace with a C.A.T4 outside its calibration period.
A future due date does not clear a damaged unit.
If a locator is dropped, flooded or gives inconsistent readings, its previous certificate cannot establish that it is still fit for the job. Follow the fault and service procedure for the model.
Read the certificate alongside the equipment.
Match the record to the actual unit and the work performed.
Useful information includes the make, model and serial number; test date; provider; scope or procedure; results; and any adjustment, defect or recommendation. Check whether the Genny has its own identifiable record and whether accessories were included.
A recommended next calibration date supports maintenance planning. It is not a promise that the unit will remain undamaged and accurate until then, or a substitute for pre-use checks.
What about an electronic self-test or eCert?
Understand the scope of the particular test. Radiodetection’s eCert can validate locating circuitry and issue a calibration certificate, but a remote test cannot inspect mechanical integrity such as a damaged seal or screen. It has a legitimate purpose; it should not be presented as either a complete physical service or an invalid certificate.
Where condition is uncertain, explain the symptoms and handling history to the service provider. Ask what examination the model needs rather than assuming every successful electronic test answers the same question.
On site or in the workshop?
Velocity Safety offers CAT & Genny calibration arrangements to suit the equipment and booking.
| Route | What to discuss |
|---|---|
| On-site visit | Make and model, fleet size, site location, access and whether the equipment can be brought together for the visit. |
| Workshop | Individual units, suspected damage, faults or work requiring further examination. Confirm delivery, return and expected turnaround before sending equipment. |
Send clear identification details and describe any fault, service warning or project deadline. Confirm the service scope, cost and available route for your units. Avoid assuming that every locator brand has the same procedure or can be dealt with at the same visit.
CAT & Genny questions.
Useful limits to keep in mind when planning the job.
What does CAT stand for?
Cable Avoidance Tool. “Genny” is the common short name for the signal generator used for active locating.
Can I use a CAT without a Genny?
Passive modes can detect some existing signals, but those signals may be absent. Radiodetection recommends using the Genny when searching for pipes and cables. Follow the method for the equipment and site.
Does a live cable always produce a Power-mode reading?
No. A cable can be energised without producing a detectable power signal. A weak or missing indication must not be treated as proof that it is dead or absent.
Will a CAT identify the exact type of pipe or cable?
Not reliably from the signal alone. A signal may be present on several conductors or transfer to a neighbouring service. Interpretation needs tracing, plans and other site evidence.
Does depth estimation prove it is safe to dig mechanically?
No. An estimate has equipment and site limitations, and the measured signal may not represent every nearby service. Follow the site’s safe excavation process and manufacturer warnings.
Is a calibration certificate valid for exactly twelve months?
It records test findings on its date and may give a recommended next due date. The maintenance interval must suit the model and programme, and damage or faults can require attention sooner.
Arrange CAT & Genny calibration.
Send the unit details and any concerns so Velocity Safety can confirm the appropriate service route.
- Make, model and serial numbers
- Quantity and location
- Faults, warnings and project deadline
Sources and technical references
- HSE HSG47: avoiding danger from underground services
- PUWER regulation 5: maintenance
- Radiodetection: using a C.A.T4
- Radiodetection: C.A.T4 and Genny4 user guide
- Radiodetection: eCert scope and limitations
- Radiodetection: C.A.T Manager eCert guidance
Sources checked 4 November 2026. Illustrations explain signal principles. They do not replace operator training, model instructions or the site’s safe system of work.
