Category Archives: Electronics

Major Three Categories That Sensors Can Be Divided Into

Sensors are intended to detect a change in a wide range of events or quantities. Most sensors are built to produce an optical output signal or electrical signal after detecting a particular type of input. There are many different sensors to match specific functions and applications.

 

Here are three of the main types of sensors:

 

Temperature

 

One of the most common types of sensors is those made to measure temperature. Thermostats are certain to feature in the home and used to detect and control the temperature of ovens, air conditioners, refrigerators and heating systems. Industrial sensors are standard in data centers and laboratories. There is a wide range of temperature sensors, but most are passive units, such as thermistors, RTDs and thermocouples. Thermocouple sensors are the most cost-effective option. They are straightforward to use and are not dependent on an excitation signal.

 

Pressure

 

Pressure sensors feature in a wide range of manufacturing and industrial systems. The sensors are used to control and measure fluid, gas or air pressure. Most are built using quartz or piezoelectric sensors. They are built to detect many different types of pressure, such as gauge pressure (atmospheric conditions), differential pressure (pressure between two points), or absolute pressure (similar to a vacuum). The analog outputs are built to measure current, such as 4-20mA, or voltage, such as 1-5V. The output information can vary to match the specific situation, and includes PSI, kg/cm2, or bars.

 

Even though the pressure sensors are mostly used in industrial systems, they also feature in designs for a wide range of consumer products, such as automotive seats and mattresses.

 

Capacitive

 

Capacitive sensing has seen a significant increase in popularity in recent years with the development of touch screen devices, such as smartphones and tablets. However, it has previously been used to detect material properties, humidity and fluid levels. This type of sensor is made using multiple layers and connects to a circuit board. The sensor has the ability to detect the location or movement of the finger on the screen. It is only able to detect capacitance related to the skin, and isn’t intended to work with fingernails.

 

When it comes to controlling capacitive sensing, the fingers do not come into direct contact with the sensing unit. A great benefit of this is the low risk of mechanical wear after regular use. Any onscreen movement is sensed by an IC. This information is digitized and passed on to a microcontroller to let the smartphone complete the particular action.

 

Cheng Tay offers a full line of thermocouple sensors including the MICROCOIL surface sensor, radio frequency thermocouple probe, tapered thermocouple probe and TRUE SURFACE thermocouple. For more details about thermocouple sensors, please don’t hesitate to click here: Cheng Tay to get information you need.

 

 

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What is a GPS Antenna?

A GPS antenna is a device that helps boost the reception signal to a GPS unit, whether it is a standalone unit or an embedded unit. Often a GPS antenna is used in a situation where the GPS unit itself is somehow removed from a line of sight to the sky, as in a car, to help the GPS “see” the sky without having to be moved. GPS antennae may be purchased for a range of budgets, or cheaper home versions can be made with fairly common components.

 

GPS, or the Global Positioning System, is a satellite system originally developed by the United States Department of Defense. It utilizes more than two dozen satellites orbiting the Earth to allow receivers on the ground or in the sky to tell exactly where they are, by receiving heads off of multiple satellites. Using this location, devices can detect not just latitude and longitude, but also altitude, and even heading and speed. For years, GPS was reserved for military use in the United States, but following a directive by President Reagan in 1983 it became open for civilian use.

 

Civilian GPS contains certain restrictions, imposed by the US government to make sure hostile forces don’t use the technology in missiles. As a result, consumer GPS isn’t capable of operating when moving at more than 515 m/s at more than 60,000 feet (18 km). Throughout the eighties and early nineties GPS was used primarily in commercial avenues, such as on fishing boats, in airplanes, or for geographic surveying. In the late nineties it began gaining popularity for consumers for hiking or for driving, and by the new millennium cars were being equipped with built-in GPS to give driving directions, and cell phones began having included GPS for directions and location.

 

A GPS unit has a built in antenna, which is usually quite small and located inside of the unit. While this will likely function in ideal circumstances, such as when in a desert moving at slow speeds or staying still, it may not work as well as one would like in more trying circumstances. A GPS unit likes to have a clear, unobstructed view of the sky, to best receive the microwave signals that allow it to communicate with satellites. For GPS units inside of cars, this can be problematic, so often an external GPS antenna will be used, mounted to the outside of the car with a magnet, and connected to the unit itself by a cable.

 

In situations such as heavy canopy cover while hiking, the small GPS antennas built into a consumer unit also may not be able to ideally communicate with the satellites. In this case, a larger, more advanced GPS antenna helps the unit overcome the environmental challenges, to give a clear signal. Similarly, moving at high velocities can overwhelm a smaller, less sophisticated antenna, and an external device can boost the signal.

 

There are a number of different types of GPS antenna, with the patch and Quad Helix styles being the most popular. Both are roughly equal in efficacy, although many people find the quad helix to have a slight bit more sensitivity. Other types of antennae include microstrips, of which the patch is one configuration, planar rings, and spiral helices.

 

Established in 1996, Cirocomm is an outstanding manufacturer of GPS antenna in the industry. We also provide various antenna series, including dielectric filter, Glonass, WIFI, GSM, NFC antenna series and more. If you are interested in and need more details about GPS antennas, welcome to visit our website and send inquiry to Cirocomm!

 

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Tips for A Fingerprint Time Attendance System to Know

Biometric Technology enables identification of person based on intrinsic physical characteristics. There are several body parts which are commonly used for biometric identification such as fingerprint, face, iris, and palm. Fingerprint is the one that most widely used for identification system. Besides showing unique pattern for each person, fingerprint also possess other attributes that make it popular biometric object such as easy to capture, consistent throughout human lifespan and enable quick verification.

Today, fingerprint time attendances have been widely used as standard office equipments. Its usage encompasses variety of purposes. It is used for controlling the physical security access, authenticating privilege for particular business process, and also recording time attendance. This article mainly discusses the last issue, which is to help you to choose fingerprint time attendance as a time attendance recorder. Here are several features that you must consider when choosing fingerprint time attendance:

  • Type of Sensor: sensor is the most important part of fingerprint time attendance. It captures the image of fingerprint before being converted into unique identification number. There are two most common types of sensors: optical sensor and silicon sensor.
  • Optical Sensor is the oldest type of sensor. It is easier to implement and relatively more stable in diverse room temperature. However its performance will be highly dependent on the clarity of the optical surface. For this reason, when choosing fingerprint time attendance with optical sensor, you should consider the coated optical sensor. The coat prevents the sensor from being touched directly and maintains the clarity of optical surface.
  • Silicon Sensor is newer technology, it constructs fingerprint image by mapping pressure or capacitance differences between the skin and the silicon chip. This technology offers several advantages like producing a more accurate fingerprint image, occupying smaller space, and requiring smaller to budget implement. However, unprotected silicon sensor will not be durable for frequent usage. Consequently, Silicon Sensor is not commonly used for public usage such as time attendance machine that will be accessed hundreds of times everyday.
  • Capacity of Fingerprint Template: capacity of fingerprint template is maximum number of fingerprint image that can be stored within the fingerprint time attendances. It is advisable to choose a fingerprint time attendance that has fingerprint template at least twice the maximum amount of employee. By having number of fingerprint template twice the amount of employee, each employee can register a backup finger if the machine has a problem for identification.
  • Capacity of Log Buffer: capacity of log buffer is the maximum number of log transactions that can be stored temporarily inside the fingerprint time attendance. Time attendance transaction log is usually stored for several days before being downloaded into database sever. Therefore, the capacity of log buffer must be several times (usually more than five times) bigger than amount of employee.
  • Identification Speed: identification speed is the average time required by fingerprint time attendance to identify a person based on his or her fingerprint pattern. The process comprises scanning the fingerprint, searching, and comparing the fingerprint pattern against its own fingerprint database. A good fingerprint time attendance should be able to identify a person in less than 1-second.
  • Standard Error: fingerprint time attendance cannot work perfectly all the time. It may wrongly identify the fingerprint pattern. There are two types of identification error: FAR (False Acceptance Rate) and FRR (False Rejection Rate). False Acceptance Rate is the percentage of machine to grant access the impostors. Meanwhile, False Rejection Rate is the percentage of machine to reject access by authorized user. Fingerprint time attendance should have as low as possible FRR and FAR. A Standard quality reference for FRR is below 0.1% and for FAR is below 0.001%.
  • Reporting Software: reporting software aggregates the transaction logs and reports in readable format. This software also helps the owner to analyze productivity of each employee. Although not all fingerprint time attendances come with built-in reporting software, it is very important component of time attendance system. It will eventually deliver the result to the owner. The quality of fingerprint time attendance is determined by its ability to deliver reports that meet the business requirements.

There are many different models, features, and capabilities of fingerprint time attendance available in the market nowadays. The most advance and versatile fingerprint time attendance may be not the most suitable for particular company’s environment. The best product is the one that fits the business and technical requirements. It means the machine must have appropriate technical specification that fits the physical environment and number of users. It must also deliver valuable information for managing the human resources productivity.

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An Overview of Video Wall Technologies

A video wall is also referred to as a data wall. It comprises a number of display panels tiled together so as to create one large screen. A data wall is connected to a video-wall processor that functions as the brain of the data wall. The processor enables the user to control the data wall using command and input devices such as a keyboard and mouse.

Data walls are a better alternative to a single large screen because they allow users to customize active display areas and are also more cost effective than a single large screen. Modern video walls with Digital Light Processing (DLP), Light Emitting Diodes (LED), and Liquid Crystal Display (LCD) technologies are widely used in control rooms and command centers.

Some common features that are expected from modern video walls are: high performance, compatibility with advanced processors, reliability, and low cost of ownership. This article elucidates the types of modern video walls seen in command centers and control rooms:

  • DLP
  • LED
  • LCD

These are the most preferred video wall systems that are compatible with the requirements of mission-critical operations. The best way to zero in on the most appropriate technology for your application would be by consulting with a reputable audiovisual systems integrator. There are some senior consultants in this industry, and some of them will provide you a free needs analysis.

People are more productive and happier in a modern and safe environment designed with their individual needs in mind. Jerry Herrington, Senior Project Consultant with Americon will help in choosing popular video walls used in control rooms and command centers for controlling and managing informations. Check out online for right LCD video wall, dispatch console and free needs analysis, space planning and cost estimate.

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Server Racks

It has been interesting over the years to see how words morph so quickly in the computer IT arena. A good example has been how the term server rack evolved from the phrases enclosure cabinet, data cabinet and computer rack that was made to hold computer hardware on 19″ EIA rack rails.

Most of these type enclosure cabinets were shallow from 20″ to 25″ deep and were basically the same for many years. Things began to change when deeper cabinets were needed as blade servers became more popular several years ago. Until blade servers entered the market, most servers were towers or 15-20″ deep that could be rack mounted in 4U-8U space.

Many popular blade servers were designed to only take up 1U-4U of space. This created the opportunity to put a lot more servers in a computer rack. An interesting problem was created however when blade servers were put in such a small “U” space. The servers became much deeper, up to 42″ deep in some cases, and also ran much hotter. Heat disperse was addressed by pulling air from the front of the server and blowing it out the back.

These deeper hot running servers no longer worked well in a conventional enclosure cabinet or computer rack and a new style computer rack was developed. This cabinet had to be deeper and allow for airflow from the front to rear to keep the servers from burning up. The industry term began to morph to server racks.

The rack rails of the server racks also changed from a long time standard of 10/32 tapped rack rails to a punched square hole that held an insert for a 6mm cage nut and screw. Dell, along with other manufactures, makes sliding rails that attach to the server rack with a special flange that fits into the square hole without the use rack screws.

Currently, server racks are made in many versions. Some have a combination plexi door with special vents cut in the frame for the front door and a screen rear door. Other server rack versions have a locking screen door in front and a double screen door in the back to save space as it opens into an aisle.

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Tips for Choosing A Fingerprint Time Attendance System

Biometric Technology enables identification of person based on intrinsic physical characteristics. There are several body parts which are commonly used for biometric identification such as fingerprint, face, iris, and palm. Fingerprint is the one that most widely used for identification system. Besides showing unique pattern for each person, fingerprint also possess other attributes that make it popular biometric object such as easy to capture, consistent throughout human lifespan and enable quick verification.

Today, fingerprint time attendances have been widely used as standard office equipments. Its usage encompasses variety of purposes. It is used for controlling the physical security access, authenticating privilege for particular business process, and also recording time attendance. This article mainly discusses the last issue, which is to help you to choose fingerprint time attendance as a time attendance recorder. Here are several features that you must consider when choosing fingerprint time attendance:

  • Type of Sensor: sensor is the most important part of fingerprint time attendance. It captures the image of fingerprint before being converted into unique identification number. There are two most common types of sensors: optical sensor and silicon sensor.
  • Optical Sensor is the oldest type of sensor. It is easier to implement and relatively more stable in diverse room temperature. However its performance will be highly dependent on the clarity of the optical surface. For this reason, when choosing fingerprint time attendance with optical sensor, you should consider the coated optical sensor. The coat prevents the sensor from being touched directly and maintains the clarity of optical surface.
  • Silicon Sensor is newer technology, it constructs fingerprint image by mapping pressure or capacitance differences between the skin and the silicon chip. This technology offers several advantages like producing a more accurate fingerprint image, occupying smaller space, and requiring smaller to budget implement. However, unprotected silicon sensor will not be durable for frequent usage. Consequently, Silicon Sensor is not commonly used for public usage such as time attendance machine that will be accessed hundreds of times everyday.
  • Capacity of Fingerprint Template: capacity of fingerprint template is maximum number of fingerprint image that can be stored within the fingerprint time attendances. It is advisable to choose a fingerprint time attendance that has fingerprint template at least twice the maximum amount of employee. By having number of fingerprint template twice the amount of employee, each employee can register a backup finger if the machine has a problem for identification.
  • Capacity of Log Buffer: capacity of log buffer is the maximum number of log transactions that can be stored temporarily inside the fingerprint time attendance. Time attendance transaction log is usually stored for several days before being downloaded into database sever. Therefore, the capacity of log buffer must be several times (usually more than five times) bigger than amount of employee.
  • Identification Speed: identification speed is the average time required by fingerprint time attendance to identify a person based on his or her fingerprint pattern. The process comprises scanning the fingerprint, searching, and comparing the fingerprint pattern against its own fingerprint database. A good fingerprint time attendance should be able to identify a person in less than 1-second.
  • Standard Error: fingerprint time attendance cannot work perfectly all the time. It may wrongly identify the fingerprint pattern. There are two types of identification error: FAR (False Acceptance Rate) and FRR (False Rejection Rate). False Acceptance Rate is the percentage of machine to grant access the impostors. Meanwhile, False Rejection Rate is the percentage of machine to reject access by authorized user. Fingerprint time attendance should have as low as possible FRR and FAR. A Standard quality reference for FRR is below 0.1% and for FAR is below 0.001%.
  • Reporting Software: reporting software aggregates the transaction logs and reports in readable format. This software also helps the owner to analyze productivity of each employee. Although not all fingerprint time attendances come with built-in reporting software, it is very important component of time attendance system. It will eventually deliver the result to the owner. The quality of fingerprint time attendance is determined by its ability to deliver reports that meet the business requirements.

There are many different models, features, and capabilities of fingerprint time attendance available in the market nowadays. The most advance and versatile fingerprint time attendance may be not the most suitable for particular company’s environment. The best product is the one that fits the business and technical requirements. It means the machine must have appropriate technical specification that fits the physical environment and number of users. It must also deliver valuable information for managing the human resources productivity.

GriyaTekno.com is building technology supplier and installer based in Indonesia. Visit us to learn more about Fingerprint Products and Access Control System in general.

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Overview of an UPS

When a power source fails, that failure can result in the loss of data, applications, capacity and other impacts. An uninterruptible power supply (UPS) is a piece of equipment that serves as a buffer between a power source and the equipment (computers, servers, machinery, etc.) that require power to operate. If a power source fails, the UPS can supply enough electricity to help avoid an operational impact. They’re typically used as an emergency resource. Though the upfront investment can be large, their availability for mission critical applications during power outages can be invaluable. Below, we’ll describe how uninterruptible power supplies work, a few ways in which they’re used and how they can be a solution for a broad range of power needs.

How An Uninterruptible Power Supply Works

There are a few types of uninterruptible power supplies (including offline, line interactive and online). Each type works differently. That being said, they work from the same fundamental principles. At its most basic, a UPS converts power from AC to DC. The power is stored within a battery while the battery is charged with a component called a rectifier. If a power source suffers an outage or the connection is severed, the battery determines how long the UPS can sustain sufficient power to maintain operational integrity. A UPS also includes a component called the inverter. The power is converted to AC before it is delivered to the equipment that needs it. Ideally, when a power source becomes unavailable, the UPS takes over immediately to provide a seamless and constant source of electrical input.

Practical Applications

The most common application for a UPS is in the event of a power failure. When a power outage occurs, it can cause a company’s entire operation to stop. This can carry a significant cost in lost production. Another use for a UPS is during voltage sags and spikes. Occasionally, a power source can experience fluctuations in voltage. While a sag in the current can dilute power from important equipment, a spike can actually damage equipment. A UPS can help regulate the flow of the electrical current.

Ultimately, the continuous flow of power provided by a UPS can be beneficial in thousands of circumstances. These can include helping computers maintain functionality, avoiding severe data loss, keeping automatic doors operating properly and countless other uses.

Power Solutions For Varying Needs

Whether you’re running a solitary computer at home or mission critical applications in a large data center, a UPS can help normalize voltage flow and provide a constant source of electricity should a power source fail. They’re available in a wide range of sizes and power capacities with prices that reflect their respective features. When the power fails, your exposure to loss of data and other impacts catapults. Invest in a robust UPS solution to mitigate that risk.

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Aerial Mapping and Surveying

Today, aerial mappings are used in dozens of different online mapping and driving direction services, including MapQuest, Google Earth, Google Maps, and specialized applications to show the location of various features. Nearly every online use for online mapping is based on aerial photographs or maps. Geographic Information Systems, or GIS, is a technology using sophisticated maps created with aerial imagery via satellites to provide information about the terrain and specific land features. This imagery is available in many different scales, in both color and black and white formats, to highlight a range of features depending on the specific application. Today there are thousands of geospatial and GIS aerial maps in use.

Aerial mapping is also very important to land surveying. While most parts of the earth have been photographed at altitude to create a map, most land surveying applications require a more detailed image of the land at a larger scale, along with the collection of more precise data points. While aerial maps for general applications are most often created through the use of satellite imagery, land surveying applications are most often undertaken with the use of an airplane or helicopter.

The main benefit of aerial methods of mapping and surveying is that they are unobtrusive, and do not require setting foot on the actual terrain. This is advantageous in situations with limited access to the land or dangerous terrain, such as areas with steep slopes. It is also important to note that aerial surveys involve the creation of three-dimensional maps through precise measurements of elevation and location, in contrast to aerial photography, which generally does not contain the same level of detail or data, although three dimensional models can be created using aerial photos.

The most common aerial surveying method is LiDAR, which uses laser beams to create a three-dimensional map or image of the land. When combined with GPS equipment, LiDAR collects information about elevation and location that can be turned into a topographical map. This date can be used in a wide variety of applications, from the creation of topographical maps to “fly through” simulations. This three-dimensional mapping system is very popular for engineers, planners, mapping technicians, GIS professionals, and surveyors. Compared to similar methods for three-dimensional information gathering, it is very accurate, relatively fast, and cost-effective.

While LiDAR and related methods represent the cutting edge of aerial surveying, the idea of aerial mapping and surveying dates back to the middle of the nineteenth century, when hot air balloons allowed surveyors to take the first aerial photographs. Aerial surveying grew in popularity after the turn of the century. The 1957 launch of Sputnik marked the beginning of the satellite imaging era.One of the earliest forms of remote sensing used for the creation of maps was photogrammery, a technique still used to the present day. This is the ability to determine measurements by using photography. Aerial photogrammery, achieved with a camera in an airplane, involves the taking of photographs of the ground every few seconds as the plane flies in a straight line. This technique was first used with film cameras, although today digital cameras are used. By matching adjacent images, a complete picture of the area can be created. Aerial photogrammery is used for terrain mapping, while close-range photogrammery can be used for a survey of building facades or other features. By taking photos from two slightly different angles, a three-dimensional model (or Digital Elevation Model) can be created from the data collected.

Aerial surveying and mapping methods are often preferred because they allow for the collection of data from a wide area in a short period of time, particularly when compared to traditional surveying methods. The digital data collected using these methods is useful for surveyors, engineers, geologists, city planners, and many other professionals who require highly precise visual maps of an area.

We at Point to Point Land Surveyors pride ourselves on accuracy, customer service and quality work delivered on time, guaranteed. Residential land surveys are a specialty.

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Introduction to the Different Types of Capacitors

A capacitor is a device used in the field of electronics that is capable of storing energy and sustaining one electric field. It consists of a pair of surfaces that are conductive, usually in the form of sheets or plates, in a position to influence the total (i.e. the electric field of all the field lines that start from one electric device and connect to another) field separated by a medium that is dielectric or vacuum. These plates, subjected to a potential difference, acquire a given electric charge, one positive and the other negative, with the total charge of zero variation.

Although from the physical point of view a capacitor stores no charge or power, but simply mechanical energy that is latent; when introduced into a circuit it behaves in practice as an element that is able to store the electrical energy it receives during the charging period, the same energy yield during the period after discharge. Due to this particular characteristic, capacitors are widely used in the field of electronics to boost the capacity of electrical devices. There are a wide variety of capacitors available in the market and they are used for commercial as well as domestic purposes.

The different types of capacitors are as follows:

Variable capacitor – These capacitors typically consist of a dielectric parallel plate and encapsulated in glass. As their electric permittivity is unity, they have a very small capacity. They are used in radio and aviation radars because of which they are regarded as very important in the field of aviation.

Mica capacitors – The mica capacitors have several properties that make them suitable for things that require a dielectric capacitor. They suffer low losses, can be wrapped in thin sheets, withstands high temperatures and are not degraded by oxidation or moisture. Aluminum is deposited on one side of the mica capacitors, forming an armature. Several of these sheets are stacked alternately by welding the ends to each of the terminals. These capacitors work well at high frequencies and high voltages, but are expensive and are gradually being replaced by other types.

Paper capacitors – These capacitors consist of waxed paper dielectric, and are subjected to any other treatment that reduces their hygroscopic and increases isolation. They are made of two strips of paper that help to prevent the pores that may arise. They are very useful in devices that require handling high voltage electricity. The paper capacitors have applications in industrial environments.

Metalized film capacitors – They are also known as self-healing capacitors. When they are faced with an overload that exceeds the dielectric strength of the capacitor, the paper tears at some point, causing a short circuit between the plates, but this short causes high current density in the torn area. This current melts the thin aluminum layer surrounding the circuit, restoring the insulation between the plates.

Electrolytic capacitors – It is a type of capacitor that uses an electrolyte, which acts as a cathode. With proper tension, the electrolyte deposits an insulating layer (which is generally a very thin layer of aluminum oxide) on the second armature or anode, thus achieving very high capacities. They cannot be operated with AC power.

Varying dielectric capacitor – These types of capacitors have a movable armature which rotates about an axis. The profile of the armature is normally such that the capacitance change is proportional to the logarithm of the rotating angle. They are used in different industrial devices that require a lot of electricity.

Looking for a capacitor for sale.

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An electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet and an armature plate. There are two main types of electric locking devices. Locking devices can be either “fail safe” or “fail secure”. A fail-secure locking device remains locked when power is lost. Fail-safe locking devices are unlocked when de-energized. Direct pull electromagnetic locks are inherently fail-safe. Typically the electromagnet portion of the lock is attached to the door frame and a mating armature plate is attached to the door. The two components are in contact when the door is closed. When the electromagnet is energized, a current passing through the electromagnet creates a magnetic flux that causes the armature plate to attract to the electromagnet, creating a locking action. Because the mating area of the electromagnet and armature is relatively large, the force created by the magnetic flux is strong enough to keep the door locked even under stress.

Typical single door electromagnetic locks are offered in both 600 lbs. and 1200 lbs. dynamic holding force capacities. A “fail safe” magnetic lock requires power to remain locked and typically not suitable for high security applications because it is possible to disable the lock by disrupting the power supply. Despite this, by adding a magnetic bond sensor to the lock and by using a power supply that includes a battery backup capability, some specialized higher security applications can be implemented. Electromagnetic locks are well suited for use on emergency exit doors that have fire safety applications because they have no moving parts and are therefore less likely to fail than other types of electric locks, such as electric strikes.

The strength of today’s magnetic locks compares well with that of conventional door locks and they cost less than conventional light bulbs to operate. There are additional pieces of release hardware installed in a typical electromagnetic locking system. Since electromagnetic locks do not interact with levers or door knobs on a door, typically a separate release button that cuts the lock power supply is mounted near the door. This button usually has a timer that, once the button is pressed, keeps the lock unlocked for either 15 or 30 seconds in accordance with NFPA fire codes. Additionally a second release is required by fire code. Either a motion sensor or crash bar with internal switch is used to unlock to door on the egress side of the door

Sourced: http://en.wikipedia.org/wiki/Electromagnetic_lock

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