Police in Taiwan used a set of spectrum analysers to catch at least three people suspected of cheating on an exam by monitoring them for mobile phone signals, a first case of its type, the equipment maker said on Wednesday.
Officers used three FSH4 analysers specially configured by the German manufacturer Rohde & Schwarz to monitor an exam in south Taiwan for prospective government workers, said senior company engineer Lai Cheng-heng.
The handheld devices are normally used to help telecom companies check the strength of phone signals, but Taiwan's National Communications Commission had asked the designer for a special order aimed at catching exam cheats.
"They didn't tell us what they were going to do. They just told us what to design, and later we found out what it was for," said Lai, who wrote the analyser software used to monitor the exam.
The 3-year-old spectrum analysers tucked into the exam monitors' belts and linked to earphones to help catch suspected cheats during an exam last month. The devices checked for signals from pagers or mobile phones near the test site.
Those sitting for the exam are supposed to shut off their mobile phones to stop test answers from reaching them via calls, text messages or vibrations.
"If they called out, they would be discovered," Lai said.
Rohde & Schwarz staffers in Taiwan know of no other such case in the world.
Spectrum analysers cannot conclusively identify specific phone users, he said, but they can narrow down the area from which a call was made. Such data is useful in conjunction with other evidence of cheating.
An officer who followed up the exam for a range of government jobs said he was unsure how many people would be formally accused of cheating. But he said the "effectiveness" of the analysers was "very high."