Some of these cameras have in-built speakers which allow the surveillance team to communicate with the people standing around the cameras. It is widely used in subways, amusement parks, transportation centers and so forth. It is used as an effective investigation tool as it helps to prevent terrorist attacks to some extent. These cameras can also be used to spot traffic jams and accidents quite easily. Undoubtedly, the invention of the Closed Circuit Camera is considered to be a breakthrough in the history of mankind.