VTR's are primarily used for perimeter door surveillance, and their major purpose is to catch criminals in the act. Many banks have successfully prosecuted robbers through video records of their crimes, and shoplifters or persons passing bad checks have also been identified. In addition, VTR evidence is nearly indisputable in court if a proper foundation is laid for its admission and expert witnesses can testify to its authenticity. VTR units can be either real time which are used in situations such as banking transactions, or time lapse which can condense up to 108 hours of real time onto tape. In general, three types of time lapse recorders are recommended for security applications: 1/2-inch reel-to-reel, 1/2-inch cassette, and 3/4-inch cassette. Of the options available on most models, manufacturers and dealers agree that a time/data generator and a sequential switcher are the most important. Other considerations include tape storage space, kind of definition needed, and length of installation. A block diagram of applications is included.