Because the label is a printed circuit on paper or film with no discrete components - it can be produced by the million on a converting line.

The tuned circuit is an etched or printed aluminium spiral with a capacitor formed between layers. There is nothing to assemble.

That makes the label thin and flexible, so it can be applied by machine, hidden under a price label, or printed as part of packaging.

The cost per label is a small fraction of an acoustomagnetic one, which dominates the economics for retailers tagging very high volumes.

It also means labels can be treated as genuinely disposable, with no expectation of recovery.

The same construction is why they are easy to detect visually and to remove - the spiral is visible through most thin packaging.

Metal, foil and liquid - the printed antenna is detuned by conductive material directly behind it.

A label applied straight onto foil packaging or a tin frequently does not respond at all.

Liquids absorb energy at this frequency, so a label on a full bottle performs far worse than the same label on an empty one.

Foil-lined bags are used deliberately to defeat detection, which is why some pedestals add metal detection.

Spacer or foam-backed labels lift the antenna clear of the surface and recover much of the performance, at higher cost.

For genuinely metallic or liquid stock, acoustomagnetic or a physical tag is usually the better answer than fighting the physics.

Less than acoustomagnetic - so wide openings need additional pedestals in the aisle rather than a wider single gap.

The practical detection width is enough for typical shop doorways and most speciality store entrances.

Supermarket-scale openings usually need pedestals placed within the entrance, creating several narrower detection zones.

Multiple pedestals must be synchronised to avoid interfering with one another, which requires interconnection.

Tag orientation matters: a flat label passing edge-on presents a much smaller signal, and detection width is quoted for favourable orientation.

Confirm coverage for the measured opening with the actual labels in use, at several heights and orientations.

The deactivator overloads a deliberately weak point in the label's circuit, permanently detuning it - so deactivation cannot be reversed.

That permanence is genuinely useful: there is no reactivation attack and no ambiguity about whether a label is live.

It also means returned goods need a fresh label before going back on the shelf, and that step is routinely forgotten.

Deactivation happens at close range, so the item has to pass near the pad - which is the argument for combining it with the scanner.

A label buried in a bulky item may sit outside the pad's reach, and those products need identifying during setup rather than at the door.

Verification, either at the pad or at the pedestal, is what turns missed deactivations from mystery alarms into a fixable process problem.

Continuous electrical noise - lighting drivers, switch-mode power supplies, refrigeration and motors - because the system transmits and listens continuously.

Modern lighting is a frequent and under-diagnosed source, particularly after a store refit changes the fittings.

The usual symptom is reduced sensitivity rather than false alarms, so the system appears to work while missing tags.

Other radio equipment operating near the frequency, including a neighbouring store's system, can also interfere.

A noise survey before installation identifies the problem when it is still cheap to solve by relocating the pedestals.

Re-survey after any significant refit. An installation that worked for years can be degraded by a new lighting scheme.

Yes - and printed or in-pack labels are much harder to find and remove than a sticker on the outside.

Labels can be inserted between packaging layers, applied under a printed label, or supplied as printable stock that carries the store's own artwork.

This is the main practical route to source tagging with radio frequency, and it is why the technology dominates in packaged goods.

An in-pack label cannot be reached at all until the packaging is broken open, which changes the offender's calculation entirely.

Placement still matters: it must not sit against foil, and it must be reachable by the deactivator at the till.

Agreeing placement with the supplier and testing on production packaging, not on a sample, is the step most often skipped.

Where the stock is metallic or liquid, where the entrance is very wide, or where the electrical environment is noisy and cannot be improved.

Grocery, hardware and off-licence stock is largely tinned, foiled or bottled, and fighting that with spacer labels is expensive and unreliable.

Very wide entrances need so many pedestals that the saving on labels is consumed by hardware and installation.

A store beside a heavy electrical installation may never achieve stable sensitivity.

High-value apparel with reusable hard tags does not benefit from the cheap label, which removes the technology's main advantage.

In all these cases acoustomagnetic is usually the better fit, and the comparison should be made on total cost including missed detections rather than on label price alone.