<P> Surveillance cameras can be a deterrent when placed in highly visible locations, and are also useful for incident verification and historical analysis . For example, if alarms are being generated and there is a camera in place, the camera could be viewed to verify the alarms . In instances when an attack has already occurred and a camera is in place at the point of attack, the recorded video can be reviewed . Although the term closed - circuit television (CCTV) is common, it is quickly becoming outdated as more video systems lose the closed circuit for signal transmission and are instead transmitting on IP camera networks . </P> <P> Video monitoring does not necessarily guarantee that a human response is made to an intrusion . A human must be monitoring the situation in real time in order to respond in a timely manner . Otherwise, video monitoring is simply a means to gather evidence to be analyzed at a later time . However, advances in information technology are reducing the amount of work required for video monitoring, through automated video analytics . </P> <P> Access control methods are used to monitor and control traffic through specific access points and areas of the secure facility . This is done using a variety of systems including CCTV surveillance, identification cards, security guards, and electronic / mechanical control systems such as locks, doors, turnstiles and gates . </P> <P> Mechanical access control systems include turnstiles, gates, doors, and locks . Key control of the locks becomes a problem with large user populations and any user turnover . Keys quickly become unmanageable, often forcing the adoption of electronic access control . </P>

Which of the following is an example of a layered defense