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Vandal-resistant switches (also referred to as vandal-proof switches) are electrical switches designed to be installed in a location (or device) and application where they may be subject to abuse and attempts to damage them, as in the case of pedestrian crossing switches. Vandal-resistant switches located on devices that are outdoors must be able to withstand extreme temperatures, dust, rain, snow, and ice. Many vandal-resistant switches are intended to be operated by the general public, and must withstand heavy use and even abuse, such as attempts to damage the switch with metal tools. These switches must also resist dirt and moisture.
Tamper-resistant switches (or tamper-proof switches) are types of vandal-resistant switches which are not intended to be operated except by authorized users. They may control special functions, such as auditing of voting machines, operation of power tools or equipment, enabling of security alarm systems (e.g., arming and disarming), or restocking of vending machines. A very commonly seen tamper-resistant switch is the ignition switch in most motor vehicles.
Vandal-resistant switches are usually protected by the use of robust materials, such as thick stainless steel or heavy-duty plastics. Some tamper-resistant switches are also protected against operation by using other approaches, such as hiding the switches behind a locked or screwed-down door-covered panel, or by requiring a key or passcode before the switch will operate the device. One widely used example of a tamper-proof switch is the ignition system of a standard car; to prevent strangers from joyriding in the car or stealing it, car ignition systems require a key to start the engine.
Pushbutton vandal-resistant switches are frequently constructed of stainless steel or other durable materials, and are mounted into panels or housing boxes made out of strong materials, such as polycarbonate plastic, aluminium, or stainless steel. In some cases, the housing may be 1⁄4 inch (6.4 mm) thick, to protect both the switch and the housing from attempts by vandals to damage the switch or housing using blunt force. The housing for vandal-proof switches is often secured using security screws (which cannot be unscrewed with regular screw drivers). The height of buttons in the panel is often minimized by using flush-mounting, to make it more difficult to pry them out, a design technique used in ATM banking machines that are located outside.
Vandal-resistant switches often need to be water and dust resistant due to their environments. Some types are potted to make them waterproof. The International Electrotechnical Commission has produced a standard, IEC 60529, which categorizes products' degrees of protection from liquids and dust using IP codes. A DIN extension of the IEC standard, DIN 40050-9 further defines Degree of Protection IP 69K as being able to withstand high-pressure washing or steam cleaning. This capability is needed in some particular applications, such as dairy milking machines, and is provided by some manufacturers' products. [1]
Vandal-resistant switches are often low-voltage, low current, so-called "signal" types intended to trigger a change in state, perhaps from "off" to "on" and vice versa. The mechanical types often have gold-plated contacts that do not corrode, to allow reliable low-power switching. [2] A few types are capable of switching 120 or 220 V AC power at several amperes, and are better suited to direct switching of the AC power to a device than the gold-plated contact switches. Heavy-duty switches often have silver or silver-plated contacts to handle higher currents. [2]
Many but not all vandal-resistant switches are momentary types; that is to say they only open or close a circuit while being depressed and revert to their inactive state when the button is released. Piezoelectric vandal-resistant switches usually fall into this category, but generally provide a pulse signal rather than staying continuously activated during the time pressure is applied, unlike their mechanical contact-based counterparts. Latching (push-on/push-off)-type vandal-resistant switches with mechanical contacts are also available, and are often used as the power switch for equipment that is used very frequently or which may be subjected to abuse.
In some cases, such as equipment used in schools, community centers, or other public places, the equipment is designed so that some or all of the switches are hidden behind a locked cover. Some public address systems are sold in tamper-resistant designs that make it harder for unauthorized members of the public to activate the system or change the settings. The switches are at the rear of the unit; only LED lights are on the front of the panel. When the unit is rack-mounted into a wall or rack unit, this means that only official personnel (who are able to access the back of the panel) can change the settings or use the unit. Another variant on this design is to cover the switches with a locked panel. In some cases, such as the sound system in a bar or club, the locked cover may be made from transparent plexiglass, so that the sound engineer can verify the sound system settings and switches (yet at the same time, the locked panel prevents mischief-minded club patrons from tampering or altering the amplifier or equalizer settings).
In some cases, the switches are placed behind a door that is secured with a screw but not locked with a key; they are out of sight and thus less likely to be interfered with. Screw-on door-covered switches are used on public address equipment that is intended to be rented out to non-professional users. The switches for some settings, such as the on-off switch for the speaker-protection limiter or a low-pitch "rumble filter" (designed to protect speakers from very low sounds), may be hidden behind a screwed-on door or metal plate.
Screwed-on covers are also widely used on children's electric and electronic toys, so that a parent can control certain settings such as the maximum speed of a toy electric ride-on car or the maximum volume of a video game.
Where lighting circuits must not be accidentally switched off (for example, school corridors), a vandal-resistant switch may be installed. These require a simple key or tool to operate, and thus discourage casual or accidental operation of the switch. [3] [4]
In some devices, the switch is built into a keyed lock mechanism, which prevents unauthorized use of the device. In this type of vandal-proof system, when the key is turned in the lock, the user can turn the equipment on. Some mobility scooters for disabled people have a locked "on-off" switch, to prevent the scooter from being driven away by vandals or joyriders while it is parked in a public place. A variant of this design is to use a computerized keypad and a secret code that activates and deactivates the switches.
The circular saw systems in home improvement stores, such as Home Depot, use a combination code keypad to prevent store patrons from using the circular saw. The power tool cannot be operated until an authorized user (e.g. a trained store employee) enters a code into the keypad.
Vandal-resistant switches (like some other types of switches) can incorporate indicator lights or LEDs to indicate circuit activation, deactivation or fault conditions. LEDs are used for this purpose in this style switch, being available in several colors and operating at low voltages. Single and ring-shaped groups of LEDs can thus show the current status of equipment or machines. In some products the LEDs can have two colors to show multiple status conditions, such as On (green) / Off (extinguished) / Fault (red).
However, many switches indicate their status by purely mechanical means, such as by the position of a toggle handle, or the visibility of a brightly painted indicator flap.
Although mechanical contact-based switches are most commonly used for general purpose electrical switching, switches that have no moving parts are generally longer-lived. Piezo and capacitance switches are the two most popular non-mechanical switch types currently available. One advantage they have over mechanical contact-based switches is that they have no moving parts to wear out. This makes them capable of lasting for tens of millions of operations. [1]
Glass reed switches use a thin metal "reed" that bends when a magnet is brought near it; since the entire unit is sealed in a glass tube, this helps protect the switch from moisture and dust that can damage regular switches.
The technology of computer keyboards includes many elements. Among the more important of these is the switch technology that they use. Computer alphanumeric keyboards typically have 80 to 110 durable switches, generally one for each key. The choice of switch technology affects key response and pre-travel. Virtual keyboards on touch screens have no physical switches and provide audio and haptic feedback instead. Some newer keyboard models use hybrids of various technologies to achieve greater cost savings or better ergonomics.
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between parts of an electrical circuit, or between different electrical circuits, thereby joining them into a larger circuit. Most electrical connectors have a gender – i.e. the male component, called a plug, connects to the female component, or socket. The connection may be removable, require a tool for assembly and removal, or serve as a permanent electrical joint between two points. An adapter can be used to join dissimilar connectors.
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
A combination lock is a type of locking device in which a sequence of symbols, usually numbers, is used to open the lock. The sequence may be entered using a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed symbols which directly interact with the locking mechanism, or through an electronic or mechanical keypad. Types range from inexpensive three-digit luggage locks to high-security safes. Unlike ordinary padlocks, combination locks do not use keys.
A safe is a secure lockable box used for securing valuable objects against theft or fire. A safe is usually a hollow cuboid or cylinder, with one face being removable or hinged to form a door. The body and door may be cast from metal or formed out of plastic through blow molding. Bank teller safes typically are secured to the counter, have a slit opening for dropping valuables into the safe without opening it, and a time-delay combination lock to foil thieves. One significant distinction between types of safes is whether the safe is secured to a wall or structure or if it can be moved around. A less secure version is usually called a cash-box.
A closure is a device used to close or seal a container such as a bottle, jug, jar, tube, or can. A closure may be a cap, cover, lid, plug, liner, or the like. The part of the container to which the closure is applied is called the finish.
Safe-cracking is the process of opening a safe without either the combination or the key.
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 prisons.
A remote keyless system (RKS), also known as remote keyless entry (RKE) or remote central locking, is an electronic lock that controls access to a building or vehicle by using an electronic remote control (activated by a handheld device or automatically by proximity). RKS largely and quickly superseded keyless entry, a budding technology that restrictively bound locking and locking functions to vehicle-mounted keypads.
Manual fire alarm activation is the process of triggering a fire alarm through a call point, pull station, or other device. This usually causes the alarm to sound the evacuation signal for the relevant building or zone. Manual fire alarm activation requires human intervention, as distinct from automatic fire alarm activation such as that provided through the use of heat detectors and smoke detectors. It is, however, possible for call points/pull stations to be used in conjunction with automatic detection as part of the overall fire detection and alarm system. Systems in completed buildings tend to be wired in and include a control panel. Wireless activators are common during construction.
An interlock is a feature that makes the state of two mechanisms or functions mutually dependent. It may be used to prevent undesired states in a finite-state machine, and may consist of any electrical, or mechanical devices or systems. In most applications, an interlock is used to help prevent any damage to the machine or to the operator handling the machine. Elevators are equipped with an interlock that prevents the moving elevator from opening its doors, and prevents the stationary elevator from moving. Interlocks may include sophisticated elements such as curtains of infrared beams, photodetectors, simple switches, and locks. It can also be a computer containing an interlocking computer program with digital or analogue electronics.
Intrinsic safety (IS) is a protection technique for safe operation of electrical equipment in hazardous areas by limiting the energy, electrical and thermal, available for ignition. In signal and control circuits that can operate with low currents and voltages, the intrinsic safety approach simplifies circuits and reduces installation cost over other protection methods. Areas with dangerous concentrations of flammable gases or dust are found in applications such as petrochemical refineries and mines. As a discipline, it is an application of inherent safety in instrumentation. High-power circuits such as electric motors or lighting cannot use intrinsic safety methods for protection.
Tamperproofing, conceptually, is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and time, the term "tamperproof" is a misnomer unless some limitations on the tampering party's resources is explicit or assumed.
NEMA connectors are power plugs and receptacles used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association. NEMA wiring devices are made in current ratings from 15 to 60 amperes (A), with voltage ratings from 125 to 600 volts (V). Different combinations of contact blade widths, shapes, orientations, and dimensions create non-interchangeable connectors that are unique for each combination of voltage, electric current carrying capacity, and grounding system.
A pressure switch is a form of switch that operates an electrical contact when a certain set fluid pressure has been reached on its input. The switch may be designed to make contact either on pressure rise or on pressure fall. Pressure switches are widely used in industry to automatically supervise and control systems that use pressurized fluids.
Silicone rubber keypads are used extensively in both consumer and industrial electronic products as a low cost and reliable switching solution.
A computer keyboard is a peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Replacing early punched cards and paper tape technology, interaction via teleprinter-style keyboards have been the main input method for computers since the 1970s, supplemented by the computer mouse since the 1980s.
Cam switches are mainly used within the low voltage range. On a shaft, switching cams are made of abrasion-resistant conductive material. By rotating the shaft, the contacts are opened or closed by the cams. Often, a plurality of cams are seated on a shaft, which simultaneously switch or switch several pairs of contacts.