The name of the job states the method. Genny and CAT — in that order — because you connect the Genny first. Said the other way round it teaches the wrong sequence, which is why the Bureau will not print it that way.
What passive detection actually detects
Power and radio modes do not search for cables. They listen for what happens to be radiating at the moment you walk past. A live loaded power cable radiates and will usually be heard. An unloaded one may not. A radio mode picks up long metallic runs re-radiating low-frequency broadcast signal, which is a happy accident of physics rather than a survey technique.
So a passive sweep answers a narrow question: what is shouting right now? It does not answer the question you actually have, which is what is down there?
What the Genny does differently
The Genny stops you waiting for a service to announce itself. You put a signal onto a known conductor — a lighting column, an LV service, a duct — and then go and find where that signal goes. You are no longer detecting; you are tracing something you chose.
That is what makes the street lighting habit worth having. Connect at a column on a tee'd off system and the signal can run the LV main and the house services with it. Connect to each property in turn instead and you can spend twenty minutes arriving at the same picture.
Why Genny first, not Genny second
Nobody argues that the Genny is optional. The argument is about order, and order is where it goes wrong. Sweep first and you build a mental map out of the loud things, then apply a signal and spend the rest of the survey reconciling the two. Connect first and everything you find afterwards is anchored to something you know the identity of.
- Voltstick anything metallic before you touch it. Test before touch, every time.
- Earth pin close to the connection point, in at a shallow angle.
- A change in tone means a good circuit. On a concrete column using capacitance there is no tone change — do not wait for one.
- Disable StrikeAlert before you locate, or you spend the next ten minutes chasing false alarms.
What about avoidance mode?
Avoidance mode runs the passive modes together so one pass covers more. It is useful, and it is still passive. It widens what you might hear; it does not change the fact that you are listening rather than asking.
Rewritten for the Bureau from the original. Method drawn from Sygma’s own training material.