Residential Access Control in Bristol

Locking device which operates by means of electric current

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An electronic lock (or electric lock) is a locking device which operates by means of electric current. Electric locks are sometimes stand-alone with an electronic control assembly mounted directly to the lock. Electric locks may be connected to an access control system, the advantages of which include: key control, where keys can be added and removed without re-keying the lock cylinder; fine access control, where time and place are factors; and transaction logging, where activity is recorded. Electronic locks can also be remotely monitored and controlled, both to lock and to unlock.

Electric locks use magnets, solenoids, or motors to actuate the lock by either supplying or removing power. Operating the lock can be as simple as using a switch, for example an apartment intercom door release, or as complex as a biometric based access control system.

There are two basic types of locks: "preventing mechanism" or operation mechanism.^{[further explanation needed]}

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The most basic type of electronic lock is a magnetic lock (informally called a "mag lock"). A large electro-magnet is mounted on the door frame and a corresponding armature is mounted on the door. When the magnet is powered and the door is closed, the armature is held fast to the magnet. Mag locks are simple to install and are very attack-resistant. One drawback is that improperly installed or maintained mag locks can fall on people,^{[dubious – discuss]} and also that one must unlock the mag lock to both enter and to leave. This has caused fire marshals to impose strict rules on the use of mag locks and access control practice in general. Additionally, NFPA 101 (Standard for Life Safety and Security), as well as the ADA (Americans with Disability Act) require "no prior knowledge" and "one simple movement" to allow "free egress". This means that in an emergency, a person must be able to move to a door and immediately exit with one motion (requiring no push buttons, having another person unlock the door, reading a sign, or "special knowledge").

Other problems include a lag time (delay), because the collapsing magnetic field holding the door shut does not release instantaneously. This lag time can cause a user to collide with the still-locked door. Finally, mag locks fail unlocked, in other words, if electrical power is removed they unlock. This could be a problem where security is a primary concern. Additionally, power outages could affect mag locks installed on fire listed doors, which are required to remain latched at all times except when personnel are passing through. Most mag lock designs would not meet current fire codes as the primary means of securing a fire listed door to a frame.^[1] Because of this, many commercial doors (this typically does not apply to private residences) are moving over to stand-alone locks, or electric locks installed under a Certified Personnel Program.^{[further explanation needed]}

The first mechanical recodable card lock was invented in 1976 by Tor Sørnes, who had worked for VingCard since the 1950s. The first card lock order was shipped in 1979 to Westin Peachtree Plaza Hotel, Atlanta, US. This product triggered the evolution of electronic locks for the hospitality industry.^{[further explanation needed]}

Electric strikes (also called electric latch release) replace a standard strike mounted on the door frame and receive the latch and latch bolt. Electric strikes can be simplest to install when they are designed for one-for-one drop-in replacement of a standard strike, but some electric strike designs require that the door frame be heavily modified. Installation of a strike into a fire listed door (for open backed strikes on pairs of doors) or the frame must be done under listing agency authority, if any modifications to the frame are required (mostly for commercial doors and frames). In the US, since there is no current Certified Personnel Program to allow field installation of electric strikes into fire listed door openings, listing agency field evaluations would most likely require the door and frame to be de-listed and replaced.

Electric strikes can allow mechanical free egress: a departing person operates the lockset in the door, not the electric strike in the door frame. Electric strikes can also be either "fail unlocked" (except in Fire Listed Doors, as they must remain latched when power is not present), or the more-secure "fail locked" design. Electric strikes are easier to attack than a mag lock. It is simple to lever the door open at the strike, as often there is an increased gap between the strike and the door latch. Latch guard plates are often used to cover this gap.

Electric mortise and cylindrical locks are drop-in replacements for door-mounted mechanical locks. An additional hole must be drilled in the door for electric power wires. Also, a power transfer hinge is often used to get the power from the door frame to the door. Electric mortise and cylindrical locks allow mechanical free egress, and can be either fail unlocked or fail locked. In the US, UL rated doors must retain their rating: in new construction doors are cored and then rated. but in retrofits, the doors must be re-rated.

Electrified exit hardware, sometimes called "panic hardware" or "crash bars", are used in fire exit applications. A person wishing to exit pushes against the bar to open the door, making it the easiest of mechanically-free exit methods. Electrified exit hardware can be either fail unlocked or fail locked. A drawback of electrified exit hardware is their complexity, which requires skill to install and maintenance to assure proper function. Only hardware labeled "Fire Exit Hardware" can be installed on fire listed doors and frames and must meet both panic exit listing standards and fire listing standards.

Motor-operated locks are used throughout Europe. A European motor-operated lock has two modes, day mode where only the latch is electrically operated, and night mode where the more secure deadbolt is electrically operated.

In South Korea, most homes and apartments have installed electronic locks, which are currently^[when?] replacing the lock systems in older homes. South Korea mainly uses a lock system by Gateman.^{[citation needed]}

The "passive" in passive electronic locks means no power supply. Like electronic deadbolts, it is a drop-in replacement for mechanical locks. But the difference is that passive electronic locks do not require wiring and are easy to install.

The passive electronic lock integrates a miniature electronic single-chip microcomputer. There is no mechanical keyhole, only three metal contacts are retained. When unlocking, insert the electronic key into the keyhole of the passive electronic lock, that is, the three contacts on the head end of the key are in contact with the three contacts on the passive electronic lock. At this time, the key will supply power to the passive electronic lock, and at the same time, read the ID number of the passive electronic lock for verification. When the verification is passed, the key will power the coil in the passive electronic lock. The coil generates a magnetic field and drives the magnet in the passive electronic lock to unlock. At the moment, turn the key to drive the mechanical structure in the passive electronic lock to unlock the lock body. After successful unlocking, the key records the ID number of the passive electronic lock and also records the time of unlocking the passive electronic lock. Passive electronic locks can only be unlocked by a key with unlocking authority, and unlocking will fail if there is no unlocking authority.

Passive electronic locks are currently used in a number of specialized fields, such as power utilities, water utilities, public safety, transportation, data centers, etc.

The programmable electronic lock system is realized by programmable keys, electronic locks and software. When the identification code of the key matches the identification code of the lock, all available keys are operated to unlock. The internal structure of the lock contains a cylinder, which has a contact (lock slot) that is in contact with the key, and a part of it is an electronic control device to store and verify the received identification code and respond (whether it is unlocked). The key contains a power supply device, usually a rechargeable battery or a replaceable battery in the key, used to drive the system to work; it also includes an electronic storage and control device for storing the identification code of the lock.

The software is used to set and modify the data of each key and lock.^[2]

Using this type of key and lock control system does not need to change user habits. In addition, compared with the previous mechanical device, its advantage is that only one key can open multiple locks instead of a bunch of keys like the current one. A single key can contain many lock identification codes; which can set the unlock permission for a single user.

A feature of electronic locks is that the locks can deactivated or opened by authentication, without the use of a traditional physical key:

Perhaps the most common form of electronic lock uses a keypad to enter a numerical code or password for authentication. Some feature an audible response to each press. Combination lengths are usually between four and six digits long.

Another means of authenticating users is to require them to scan or "swipe" a security token such as a smart card or similar, or to interact a token with the lock. For example, some locks can access stored credentials on a personal digital assistant (PDA) or smartphone, by using infrared, Bluetooth, or NFC data transfer methods.

As biometrics become more and more prominent as a recognized means of positive identification, their use in security systems increases. Some electronic locks take advantage of technologies such as fingerprint scanning, retinal scanning, iris scanning and voice print identification to authenticate users.

Radio-frequency identification (RFID) is the use of an object (typically referred to as an "RFID tag") applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader. This technology is also used in some modern electronic locks. The technology has been approved since before the 1970s, but has become much more prevalent in recent years due to its usages in things like global supply chain management and pet microchipping.^[3]

• Access badge
• Common Access Card (CAC)
• Credential
• Electric strike
• Electromagnetic lock
• Keycard
• Physical security

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An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which functions independently of the public telephone network.^[1] Intercoms are generally mounted permanently in buildings and vehicles, but can also be detachable and portable. Intercoms can incorporate connections to public address loudspeaker systems, walkie talkies, telephones, and other intercom systems. Some intercom systems incorporate control of devices such as signal lights and door latches.

Intercoms are used on a wide variety of properties; from houses that only require one connection between a resident and the property's entrance to multi-unit apartments that require intercom hardware to be installed in every individual apartment.^[1] Some are equipped with video^[1] and its wiring (electrical installation) can be connected to the outside with a few pairs (4-6 pairs) while controlling an electric strike. The latest generations are even compatible with computers and some models include TCP/IP compatibility.

Traditional intercoms and public address systems are composed entirely of analogue electronics components but many new features and interfacing options can be accomplished with new intercom systems based on digital connections. Video signals can be carried as well as voice. Digital intercom stations can be connected using Cat 5 cable and can even use existing computer networks as a means of interfacing distant parties. Intercom cameras can be used in modern offices and hotels.

Many schools and office buildings now use audio / video systems to identify visitors trying to gain access to a locked building and can be interfaced with the building's access control system.

Besides fixed locations, intercom systems are used on many types of vehicles including trains, watercraft, aircraft and armoured fighting vehicles.

Portable intercoms are commonly used by special event production crews and professional sports teams. Performing arts venues such as theaters and concert halls often have a combination of permanently mounted and portable intercom elements. Motorsports race tracks often have both portable and permanent intercom stations mounted at critical points around the racecourse for use by race officials and emergency medical technicians.

Portable intercoms are also used for motorcycle communication, for example between motorcyclist and passenger, bike-to-bike communication or communication within a pack of riders. Intercom mounting systems can be attached to most motorcycle helmets.^[2] Several different types of technologies can be used, including various types of citizens band radio like for example PMR446, Bluetooth, or dynamic mesh communication (DMC) which is a mesh based intercom system developed for motorcycle communication.^[3]

Intercom installers, suppliers, and manufacturers often use the following terms to refer to intercom components.

• Master station or base station: These units control the whole system. Master stations initiate calls to substations and can be configured to make announcements that are transmitted over the entire intercom system.
• Substation: Units that initiate calls with a master station, but are not capable of initiating calls with any other stations. Substations are also known as slave units.
• Door station: Like substations, door stations are only capable of initiating a call to a master station. They are typically weather-proof.
• Intercom station: A full-featured remote unit that is capable of initiating and receiving party-line conversation, individual conversations, and signalling. May be rack-mounted, wall-mounted or portable.
• Wall mount station: Fixed-position intercom station with built-in loudspeaker. May have flush-mounted microphone, hand-held push to talk microphone or telephone-style handset.
• Belt pack: Portable intercom station worn on the belt such as an interruptible feedback (IFB) with an earpiece worn by talent.
• Handset: Permanent or portable telephone-style connection to an intercom station. Holds both an earpiece and a push to talk microphone.
• Headset: Portable intercom connection from a belt pack to one or both ears via headphones with integrated microphone on a boom arm. Connects to a belt pack.
• Paging signal: An audible and/or visual alert at an intercom station, indicating that someone at another station wants to initiate a conversation.
• Power supply: Used to feed power to all units. Often incorporated into the design of the base station.
• Telephonic: Intercom systems that utilize a transmitter (talk) and receiver (listen) to communicate, similar to standard telephone systems.
• Amplified: Intercom systems that utilize a single speaker to transmit and receive communications.
• Amplifier: An intercom system's main or central component, responsible for switching or connecting communication paths between master and substations. In addition, amplifiers distribute or switch power to auxiliary connected devices, such as door strikes, to allow entry.

While every intercom product line is different, most analogue intercom systems have much in common. Voice signals of about a volt or two are carried atop a direct current power rail of 12, 30 or 48 volts which uses a pair of conductors. Signal light indications between stations can be accomplished through the use of additional conductors or can be carried on the main voice pair via tone frequencies sent above or below the speech frequency range. Multiple channels of simultaneous conversations can be carried over additional conductors within a cable or by frequency- or time-division multiplexing in the analogue domain. Multiple channels can easily be carried by packet-switched digital intercom signals.

Portable intercoms are connected primarily using common shielded, twisted pair microphone cabling terminated with 3-pin XLR connectors. Building and vehicle intercoms are connected in a similar manner with shielded cabling often containing more than one twisted pair.

Digital intercoms use Category 5 cable and relay information back and forth in data packets using the Internet protocol suite.

Intercom systems are widely used in TV stations and outside broadcast vehicles such as those seen at sporting events or entertainment venues. There are essentially two different types of intercoms used in the television world: two-wire party line or four-wire matrix systems. In the beginning, TV stations would simply build their own communication systems using old phone equipment. However, today there are several manufacturers offering off-the-shelf systems. From the late 1970s until the mid-90s, the two-wire party line-type systems were the most popular, primarily due to the technology that was available at the time. The two-channel variety used a 32-volt impedance-generating central power supply to drive external stations or belt packs. This type of format allowed the two channels to operate in standard microphone cable, a feature highly desired by the broadcasters. These systems were very robust and simple to design, maintain and operate but had limited capacity and flexibility as they were usually hardwired. A typical user on the system could not choose whom to talk to. He would communicate with the same person or group of people until the system was manually reconfigured to allow communication with a different group of people. Two-wire routers or source assignment panels were then implemented to allow quick re-routing. This reconfiguration was usually handled at a central location, but because voltage is used on the circuit to power the external user stations as well as communicate, there would usually be a pop when the channels were switched. So while one could change the system on-the-fly, it was usually not desirable to do so in the middle of a production, as the popping noise would distract the rest of the television crew.

In the mid-90s four-wire technology started gaining more prominence due to the technology getting cheaper and smaller. Four-wire circuit technology had been around for quite some time but was very expensive to implement. It usually required a large footprint in the physical television studio, thus was only used at very large television stations or television networks.

For installations where it is not desirable or possible to run wires to support an intercom system, wireless intercom systems are available. There are two major benefits of a wireless intercom system over the traditional wired intercom. The first is that installation is much easier since no wires have to be run between intercom units. The second is that you can easily move the units at any time. With that convenience and ease of installation comes a risk of interference from other wireless and electrical devices. Nearby wireless devices such as cordless telephones, wireless data networks, and remote audio speakers, as well as structural features in your building, can all interfere. Electrical devices such as motors, lighting fixtures and transformers can cause noise. There may be concerns about privacy since conversations may be picked up on a scanner, baby monitor, cordless phone, or a similar device on the same frequency. Encrypted wireless intercoms can reduce or eliminate privacy risks, while placement, installation, construction, grounding and shielding methods can reduce or eliminate the detrimental effects of external interference. The United States and Canada have several frequency ranges for wireless intercom systems and other wireless products. They are 49 MHz, FM band (200–270 kHz), 494–608 MHz, 900 MHz, 2.4 GHz, 5.8 GHz, and MURS (150 MHz). IP Intercoms are now appearing that connect a Master to an IP Substation elsewhere on the Internet, via an Ethernet port. Wireless intercoms can also run over a mesh network that allows near-instant communication throughout a house.

Power line communication units that send signal over house wiring have been referred to as "wireless" intercoms. Though they are technically wired intercoms, they are based on existing wiring and thus require no additional wires.

Some telephones include intercom functions that enable paging and conversation between instruments of similar make and model. Examples include Panasonic model KX-TS3282W(/B), AT&T models 945 and 974, and TMC model ET4300.

A single device can add intercom functionality to multiple standard telephones on a common phone line, even of different makes and models. Installation effort is minimal, and is not vulnerable to the radio interference and security issues of wireless systems. The Add-A-Com Whole House Intercom for Standard Telephone Systems is such a device. Intercom paging is accomplished by sounding a distinctive ring from all telephones after any phone is taken briefly off hook. After paging, any number of phones may converse. The device temporarily disconnects the external phone line during intercom use, and reconnects when all phones are again on hook. During intercom use, an external call’s ringing signal can be heard in the earpiece.

Many key telephone systems for office use provide access to multiple outside lines plus an intercom, where the latter appeared as if it were one of the individually-selectable lines. The Western Electric Model 207 and Model 6A intercoms were designed for integration into such key system multiline installations, providing one or two simultaneous intercom calls respectively.

A cell phone network intercom is an outdoor device that communicates wirelessly over the cell phone network with any landline or mobile phone worldwide. Often called GSM intercoms, they initially used the Global System for Mobile Communications standard, and the intercoms were first released in European countries. This standard is now used globally, though in the United States, primarily AT&T, T-Mobile, and a few other providers use GSM, while Sprint and Verizon used CDMA (Code Division Multiple Access) technology. Modern cell phone intercoms support all carriers and the latest technologies. Commonly installed at gates or doors, they are popular because they eliminate the need for wiring, except for power.^[4]

Wikimedia Commons has media related to Intercoms.

• Courtesy telephone, a telephone for relaying messages to a specific person after being notified via a public address system, or for customers to seek information
• Door phone, electronic device for communication with someone outside a building
  • Video door-phone, audiovisual communication device enabling visual identification of a visitor
• Public address system, a system for distributing the voice of an announcer over a large area
• Speaking tube, an air pipe through which speech can be transmitted over an extended distance
• Tank phone, similar device used in Tanks and Armoured vehicles
• Voice chat in online gaming