A radar detector detector (RDD) is a device used by police to determine if a vehicle is fitted with, and using, a radar detector. RDD's were brought about by the need for law enforcement officers to determine if a driver was using a radar detector in a state or country where they are illegal.

Early RDD's included the VG-2 which "listened" for the radio frequency leakage (around 10.5Ghz) emitted by the local oscillator - inherent to all

Radar Detector manufacturers counted this threat by in tern, "listening" for the VG-2 and shutting down the RD if the VG-2 was detected. This cat and mouse game continued, when RD manufacturers shifted the local oscillator frequency of their detectors to a frequency outside the range of the VG-2. These detectors were known as VG-2 immune.

Stealth Micro Systems (SMS) of Australia developed the Spectre RDD and later followed with upgrades, the Spectre 2 and Spectre 3. The Spectre II and III were so successful, that many law enforcement agencies around the world submitted large orders for these devices.

SMS named their local version of the Spectre RDD the Stalcar, and as per the international model, released the Stalcar 2 and 3. The use of radar detectors is illegal in most Eastern States of Australia, so the local sales of the Stalcar were well received.

Only a handful of US states ban the use of radar detectors, although RD's are illegal in 18 wheelers nation wide. The use of Spectre RDD's in these areas had the RD manufacturers beat....until Beltronics released the STi.

The Bel STi one of the very few RDs on the market to be totally immune to all known brands of Radar Detector Detectors. Instead of shifting the lo frequency leak, as was past measures to defeat the RDDs, the Bel STi (and other stealth radar detectors) completely conceals all lo emissions. This has rendered the Spectre / Stalcar useless against this type of detector.

It should be noted that many Radar Detectors cannot be detected by the old VG-2 radar detector detector (RDD), which is often referred to as "shadow technology". This is useless against modern RDDs as the VG-2 is hardly used anymore, and is replaced by the Spectre / Stalcar.