Vandal resistant switch
Encyclopedia
Vandal resistant switches (sometimes referred to as vandal proof switches or tamper-proof switches) are electrical switch
es designed to be installed in a location (or device) and application where they may be subject to vandalism
or tampering, as in the case of pedestrian crossing switches, or fraudulent or unauthorized use, as in the case of vending machine switches. Vandal resistant switches that are located on devices that are accessible to the public or which are located outside also have to be able to withstand dust, rain, snow, and frequent operation.
Pushbutton vandal-resistant switches are frequently constructed of stainless steel
or other durable metals and 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" 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. Some vandal-resistant switches are protected against tampering 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.
-plated contacts that do not corrode to allow reliable low-power switching. A few types are capable of switching 120 or 220 Volt
AC power at several Amperes. These types are better suited to on-off switching of the AC power to a device than the gold-plated contact switches. They often have silver
or silver-plated
contacts to handle the higher currents that they are specified to switch. Piezo switch
types are another of the popular types of vandal resistant switches.
Most, 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.
or stainless steel
, and 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.
In some cases, the switches are placed behind a door that is secured with a screw. While this type of "hidden switch" is not locked with a key, it is out of sight and thus it is less likely that most users of the device will try to use them. 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.
s 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 LED
s can have two colors to show multiple status conditions, such as On(e.g. green)/Off(extinguished)/Fault(red).
and capacitive 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. Glass reed switch
es 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.
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....
es designed to be installed in a location (or device) and application where they may be subject to vandalism
Vandalism
Vandalism is the behaviour attributed originally to the Vandals, by the Romans, in respect of culture: ruthless destruction or spoiling of anything beautiful or venerable...
or tampering, as in the case of pedestrian crossing switches, or fraudulent or unauthorized use, as in the case of vending machine switches. Vandal resistant switches that are located on devices that are accessible to the public or which are located outside also have to be able to withstand dust, rain, snow, and frequent operation.
Pushbutton vandal-resistant switches are frequently constructed of stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
or other durable metals and mounted into panels or housing boxes made out of strong materials, such as polycarbonate
Polycarbonate
PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...
plastic, aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
. In some cases, the housing may be 1/4" 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. Some vandal-resistant switches are protected against tampering 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.
Electrical characteristics
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 goldGold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
-plated contacts that do not corrode to allow reliable low-power switching. A few types are capable of switching 120 or 220 Volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
AC power at several Amperes. These types are better suited to on-off switching of the AC power to a device than the gold-plated contact switches. They often have silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
or silver-plated
Plating
Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years, but it is also critical for modern technology...
contacts to handle the higher currents that they are specified to switch. Piezo switch
Piezo switch
A piezo switch is an electrical switch based on the piezoelectric effect.The folcharge generated by the piezoelectric element in the switch is typically used to turn on an integrated semiconductor device such as a field effect transistor , causing the switch assembly's output to be active, or "on"...
types are another of the popular types of vandal resistant switches.
Most, 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
Piezoelectricity
Piezoelectricity is the charge which accumulates in certain solid materials in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure...
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.
Mechanical characteristics
Vandal resistant switches share a few general mechanical characteristics. They are made of durable materials such as machined brassBrass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
, and often need to be water and dust resistant due to their environments. Some types are potted
Potting (electronics)
In electronics, potting is a process of filling a complete electronic assembly with a solid or gelatinous compound for resistance to shock and vibration, and for exclusion of moisture and corrosive agents...
to make them waterproof. The International Electrotechnical Commission
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
has produced a standard, IEC 60529, which categorizes products' degrees of protection from liquids and dust using IP codes. A DIN
Din
DIN or Din or din can have several meanings:* A din is a loud noise.* Dīn, an Arabic term meaning "religion" or "way of life".* Din is one of the ten aspects of the Ein Sof in Kabbalah ....
extension of the IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
standard, DIN 40050-9 further defines Degree of Protection IP 69K as being able to withstand high-pressure washing
Pressure washer
A pressure washer is a high pressure mechanical sprayer that can be used to remove loose paint, mold, grime, dust, mud, and dirt from surfaces and objects such as buildings, vehicles, and concrete road surfaces. The volume of a pressure washer is expressed in Gallons Per Minute, which is designed...
or steam cleaning
Vapor Steam Cleaners
Vapor steam cleaners or steam vapor systems are cleaning appliances or devices that use steam to quickly dry, clean, and sanitize inanimate surfaces. Often the process is effective enough to disinfect or even sterilize the surfaces...
. This capability is needed in some particular applications, such as dairy
Dairy
A dairy is a business enterprise established for the harvesting of animal milk—mostly from cows or goats, but also from buffalo, sheep, horses or camels —for human consumption. A dairy is typically located on a dedicated dairy farm or section of a multi-purpose farm that is concerned...
milking machines, and is provided by some manufacturers' products.
Hidden switches
In some cases, such as equipment used in schools, community centers, or other public places, the equipment is designed so that all of the switches, or some of the switches, are hidden or placed 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. Some tamper-proof public address systems are designed so that 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 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. While this type of "hidden switch" is not locked with a key, it is out of sight and thus it is less likely that most users of the device will try to use them. 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.
Locked switches
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 sccoter 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 major hardware stores use a combination code keypad to prevent store patrons from using the circular saw. The buttons that activate the circular saw do not activate the blade until an authorized user (e.g., a trained store employee) enters the code into the keypad.Illuminated (indicator) types
Vandal resistant switches (like some other types of switches) can incorporate indicator lights or LEDLEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s 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 LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s can have two colors to show multiple status conditions, such as On(e.g. green)/Off(extinguished)/Fault(red).
Non-mechanical types
Although mechanical contact-based switches are most commonly used for general purpose electrical switching, switches that have no moving parts are generally longer-lived. PiezoPiezo switch
A piezo switch is an electrical switch based on the piezoelectric effect.The folcharge generated by the piezoelectric element in the switch is typically used to turn on an integrated semiconductor device such as a field effect transistor , causing the switch assembly's output to be active, or "on"...
and capacitive 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. Glass reed switch
Reed switch
The reed switch is an electrical switch operated by an applied magnetic field. It was invented at Bell Telephone Laboratories in 1936 by W. B. Ellwood. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope...
es 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.
Applications
- Public interactive kioskInteractive kioskAn Interactive kiosk is a computer terminal featuring specialized hardware and software designed within a public exhibit that provides access to information and applications for communication, commerce, entertainment, and education....
s that provide tourist information or government forms - ElevatorElevatorAn elevator is a type of vertical transport equipment that efficiently moves people or goods between floors of a building, vessel or other structures...
buttons and security switches - Pedestrian crossing signal activation switches
- Intercom "push-to-talk" devices at the entrance to apartment buildings
- Electronic door switches for garages and mechanical gates
- Parking lot ticket machineTicket machineA ticket machine, also known as a ticket vending machine , is a vending machine that produces tickets. For instance, ticket machines dispense train tickets at railway stations and tram tickets at some tram stops and in some trams...
s and computerized ticket paying stations - Automatic foodFoodFood is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...
and drink vending machines - Public address systems in schools, community centers, and bars
- Rental equipment that may be subjected to heavy use