The Perceptrak system, which has been installed in car parks, stairwells and streets, has 18 different sets of criteria such as "fast moving car" and "converging people" that activate it.
Once it recognises something suspicious or unusual, it sends an alert to the city centre's control room, where the security officer on duty must take appropriate action.
To date, the city council has installed 142 cameras which are monitored 24 hours a day. However, the city council has access to 1000 cameras with plans to implement Perceptrak on up to 600.
Ray Stead, CCTV manager at Portsmouth City Council, said: "Following a successful trial period in 2006, we decided to install the system on a more permanent basis because of the quantifiable benefits to the control room outcomes."
The system was provided to the city council for free.
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