2009, there were an estimated 15,000 cctv systems in Chicago, many linked to an integrated camera network. "ET_SRB Cam dd" (PDF). 28 In particular, the estimated effects may be biased if cctv is introduced in response to crime trends. 121 Previous generations of wireless security cameras relied on analog technology; modern wireless cameras use digital technology which delivers crisper audio, sharper video, and a secure and interference-free signal. Freedom of Information and Protection of Privacy Act Archived September 24, 2007, at the Wayback Machine. 79 The Cheshire figure is regarded as more dependable than a previous study by Michael McCahill and Clive Norris of UrbanEye published in 2002. "Eye on the City: Do Cameras Reduce Crime?". Special cameras for some of these purposes include line-scan cameras and thermographic cameras which allow operators to measure the temperature of the processes. Opponents of cctv point out the loss of privacy of people under surveillance, and the negative impact of surveillance on civil liberties. On average, professional level software is offered at US75, with some of them requiring annual fees for membership. See also edit Another estimate put the number at about 100 million worldwide in 2011. Furthermore, while it is true that there may be scenarios wherein a person's right to public privacy can be both reasonably and justifiably compromised, some scholars have argued that such situations are so rare as to not sufficiently warrant the frequent compromising of public privacy. Joe Walcott in 1948. Desk in one of the regional control-rooms of the National Police in the Netherlands in 2017. 123 Other towns have had such cameras installed.