Closed-circuit television (CCTV), also known as video surveillance, is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point-to-point (P2P), point-to-multipoint (P2MP), or mesh wired or wireless links. Even though almost all video cameras fit this definition, the term is most often applied to those used for surveillance in areas that require additional security or ongoing monitoring (Videotelephony is seldom called "CCTV").
Surveillance of the public using CCTV is common in many areas around the world. Video surveillance has generated significant debate about balancing its use with individuals' right to privacy even when in public.
In industrial plants, CCTV equipment may be used to observe parts of a process from a central control room, especially if the environments observed are dangerous or inaccessible to humans. CCTV systems may operate continuously or only as required to monitor a particular event. A more advanced form of CCTV, using digital video recorders (DVRs), provides recording for possibly many years, with a variety of quality and performance options and extra features (such as motion detection and email alerts). More recently, decentralized IP cameras, perhaps equipped with megapixel sensors, support recording directly to network-attached storage devices, or internal flash for completely stand-alone operation.
By one estimate, there will be approximately 1 billion surveillance cameras in use worldwide by 2021.[needs update] About 65% of these cameras are installed in Asia. The growth of CCTV has been slowing in recent years.[unreliable source?] The deployment of this technology has facilitated significant growth in state surveillance, a substantial rise in the methods of advanced social monitoring and control, and a host of crime prevention measures throughout the world.
A security alarm is a system designed to detect intrusions, such as unauthorized entry, into a building or other areas, such as a home or school. Security alarms protect against burglary (theft) or property damage, as well as against intruders. Examples include personal systems, neighborhood security alerts, car alarms, and prison alarms.
Some alarm systems serve a single purpose of burglary protection; combination systems provide fire and intrusion protection. Intrusion-alarm systems are combined with closed-circuit television surveillance (CCTV) systems to record intruders' activities and interface to access control systems for electrically locked doors. There are many types of security systems. Homeowners typically have small, self-contained noisemakers. These devices can also be complicated, multirole systems with computer monitoring and control. It may even include a two-way voice which allows communication between the panel and monitoring station.
Guildford (/ˈɡɪlfərd/ (listen)) is a town in west Surrey, around 27 mi (43 km) southwest of central London. As of the 2011 census, the town has a population of about 77,000 and is the seat of the wider Borough of Guildford, which had around 148,998 inhabitants in 2019. The name "Guildford" is thought to derive from a crossing of the River Wey, a tributary of the River Thames that flows through the town centre.
The earliest evidence of human activity in the area is from the Mesolithic and Guildford is mentioned in the will of Alfred the Great from c. 880. The exact location of the main Anglo-Saxon settlement is unclear and the current site of the modern town centre may not have been occupied until the early-11th century. Following the Norman Conquest, a motte-and-bailey castle was constructed, which was developed into a royal residence by Henry III. During the late Middle Ages, Guildford prospered as a result of the wool trade and the town was granted a charter of incorporation by Henry VII in 1488.
The River Wey Navigation between Guildford and the Thames was opened in 1653, facilitating the transport of produce, building materials and manufactured items to new markets in London. The arrival of the railways in the 1840s attracted further investment and the town began to grow with the construction of its first new suburb at Charlotteville in the 1860s. The town became the centre of a new Anglican diocese in 1927 and the foundation stone of the cathedral was laid in 1936. Guildford became a university town in September 1966, when the University of Surrey was established by Royal Charter.
Guildford is surrounded on three sides by the Surrey Hills Area of Outstanding Natural Beauty, which severely limits its potential for expansion to the east, west and south. Recent development has been focused to the north of the town in the direction of Woking. Guildford now officially forms the southwestern tip of the Greater London Built-up Area, as defined by the Office for National Statistics.