CCTV TERMS

AGC: Automatic Gain Control; a circuit that is designed to control the gain of amplifiers within a camera to maintain a desired output with a varying input.

AUTO BEAM: A circuit within a camera that compensates for tube aging by adjusting the amount or beam current flowing to maintain a discharged tube

AUTO BLACK: The ability of a camera to maintain a reference point that is considered to be the blackest portion of the viewed scene.

ASPECT RATIO: The ratio of width to height of CCTV picture commonly 4:3.

BANDWIDTH: The # of cycles per second detailing the difference between the upper and the lower operation frequencies Typically the higher the operation bandwidth the greater the resolution.

BLACK LEVEL: The darkest portion of the video signal typically set at a level which is 270-300mv above the sync level.

BLOOMING: The overflow of high white signals appearing as a defocused blur on the monitor screen.

C-MOUNT: The standard of CCTV for mounting lenses The C-Mount is a threaded mount consisting or a 1 inch diameter barrel with 32 threads per inch.

CCIR: An abbreviation for Consultative Committee for International radio. A group that worked to setup the operational requirements for European Radio and Television Standards.

CCTV: An abbreviation for Closed Circuit Television which is a system that transmits television signals over a closed ( non-broadcast) system.

CCD: An abbreviation for Charged Coupled Device. This solid state device is used to transfer light images into electronic information which in a camera is used to reproduce the image into a video signal.

COAX: The cable used to transfer the composite video signal from the camera to the monitor. This Coaxial cable consists of a conductor surrounded by a shield and isolated from the shield.

COMPOSITE VIDEO SIGNAL: The signal used to transmit picture information from the camera to the monitor. This signal is a combination or composite of video information pedestal levels and synchronization signals.

db:. An abbreviation of DECIBEL. A term used to measure the power or voltage ratios of two signals.

EIA: An abbreviation for Electronic Industry Association, which setup criteria and standards for commercial broadcast television equipment.

FIBER OPTICS: The term used for optical fiber, or glass fibers used to transmit light from point to point. Used in CCTV to transmit camera signals over greater distances and through high magnetic or electrically Interfering areas.

FIELD: One half of a complete video image. The US standard for television consists of a scan rate of 60 fields per second. Two fields are required to produce a complete image or frame.

FIELD OF VIEW: The maximum viewed image achieved by a lens referred to as an angle-of view.

FOCAL LENGTH: The measurement in a lens that corresponds to the distance from the imager focal point to the principal point of the lens.

FOCAL POINT: The location on an imager where the lens focuses

FO0TCANDLE: A unit of measurement used to describe the amount of light being distributed onto a surface. Typically used to describe a source of light.

FO0TLAMBERT: A unit of measurement used to describe the amount of light reflected from a surface.

FRAME: A complete picture generated by a camera/monitor system. The frame consists of two fields of information each being produced at a rate of 60 fields per second.

F-STOP: A term used to describe the speed of a lens, or its ability to pass light through its lensing and onto the imager. It is determined by dividing the focal length of the lens by the diameter.

GAMMA: A term used to describe the amount of contrast in a picture generated from a camera. Gamma correction within a camera allows the camera/monitor system to reproduce accurate contrast levels equal to the viewed scene.

GENLOCK: The term used to describe the ability of a camera to lock it s internal synchronization to an external source.

GRAY SCALE: A visual chart showing bars varying from white to black going through steps of gray commonly in 10 stages.

IMAGE BURN: The term used to describe the result of excessive light upon a imager's surface. This will appear as an image which persists on the monitor screen after the cameras viewed image has changed. Image burns can be present on both camera image devices and monitor screens.

INTERLACE: Interlace refers to the scanning method used by the two fields that produce the single frame of information Field one scans the odd lines and field two scans the even. Two types of interlacing are commonly used. CCTV system cameras random, and 2 to 1. random interlacing has a random and not a defined starting point for the scan line. 2 to 1 interlace has a defined starting scan point and will offer a more stable picture

IRIS: A mechanism within the lens that controls the amount of light that will pass through the lens.

ISIT: An abbreviation for intensified Silicon intensified Target. Image pickup tube used for extremely low light applications. A SIT tube with an additional intensifier stage coupled to it to increase its sensitivity.

LAG: The Presentation of a blurred image, typically from a high white object due to the inability of a pickup device to remove the electrical charge from its surface at the scanning rate.

LOOP THROUGH: The term used to describe the non-terminating of a video signal. A loop through device will allow the signal to pass through onto another device where it will eventually be terminated. Commonly loop through devices will provide 2 connection points for the coax cable and offer a means to terminate (75 ohms) or loop through (Hi-Z).

MICROWAVE: A transmission medium which uses transmitter and receives and transmits video/communication signals through space with no connection between the transmitter/receiver. A line of sight is required for this medium.

MONITOR: A device used to reproduce a visual image from a composite video signal.

MULTIPLEXER: A term used for a device that can combine multiple video signals onto a single monitor transmission medium or recorder.

N D FILTER: NEUTRAL DENSITY filter; an optical filter to evenly reduce the intensity of light

NTSC: An abbreviation for National Television Standard Committee. The committee that established the standards for the U.S. television industry

PAL: An abbreviation for Phase Alternating Line. A European standard for color systems where the color reference signal is alternated in phase from one line to the next to minimize color hue errors that could occur in color signal transmission.

PAN AND TILT: A device that allows camera movement in both the left/right(pan) and the up/down (tilt) directions .

PEDESTAL: A portion of the composite video signal that refers to the voltage distance between the upper portion of the sync signal and the blackest portion of the video also referred to as the black level.

PIXEL: A segment of a imaging device used to convert light information into an electronic charge equal to the amount of light striking the segment.

RASTER: The area of a image tube that Is scanned by the electron beam.

RASTER BURN: The area of a image tube where due to repetitive scanning has caused a visible outline to form on the tube.

RESOLUTION: the ability of a CCTV system to distinguish and reproduce fine detail in a viewed scene.

SCANNING: The action of moving an electron beam across the imager or display tube.

SENSITIVITY: A term used to describe the required light level needed to produce a desired signal.

SIGNAL TO NOISE: The ratio of the video level to the amount of noise in the signal.

SIT: An abbreviation for Silicon Intensified Target. Imager designed for low light applications. A silicon target imager with a intensifier coupled to it.

SYNC: An abbreviation for SYNChronization referring to the signals produced by the camera, and used by the monitor to accurately reproduce the viewed image onto the monitor screen.

TARGET: The surface of a image tube which collects light information and is scanned by the. electron beam to produce a signal corresponding to the light

TERMINATION: The term used to describe the end of line requirements for CCTV cable runs. In CCTV the termination is 75 ohms which corresponds to the characteristic impedance of the coax.

TRANSFER SMEAR: The visual appearance of a white line typically from the top to the bottom of the screen due to the inability of a image device to handle excessive light.

WHITE CLIPPER/LIMITER: The circuit within a camera that limits the amplitude of white signals

Electronic Access Control Terms

ELECTRONIC ACCESS CONTROL:
Electronic access control systems have become the most important aspect of many company's security measures in the last decade. Improvements and cost reductions in the microprocessor have made access control affordable for large and small businesses alike, while improving systems performance.
Surprisingly,, anyone who understands basic wiring and has a working knowledge of computers can successfully install today's access control systems, if they carefully follow the manufacturer's application recommendations.
Electronic access control provides an extremely effective means of granting entry to personnel who need it, while maintaining the security of the building. Access control systems can often reduce costs of guard services and re-keying lock-sets, while providing a higher level of security. Access control systems offer the following advantages:

Employees who have left can be removed from the system. Once they are removed, the employee no longer has access, even though they may still have the access card.
An audit trail is provided for management tracking and reporting of who entered and/or left a particular area at a particular time. Tracking of invalid attempts is also provided in many systems to allow management to determine if employees are attempting to enter areas they are not permitted into, or whether employees are attempting to get into areas at the wrong time.

Access Control Applications:

Computer rooms, office areas, building entries, storage rooms, electrical service rooms, data communications rooms, telephone closets, parking areas, elevators, warehouses, nuclear facilities, and other areas are typically protected by access control systems. Small and large companies have needs for employee control.

READER TECHNOLOGIES:

Magnetic Stripe

Magnetic stripe cards can be identified by a black strip on the outside face of the card. Bank credit cards and ATM cards are typically magnetic stripe cards. Magnetic stripe cards are usually the least expensive choice of reader technologies. They are also easily duplicated, but are considered more secure than barcode (refer to barcode for details).
Magnetic stripe cards are encoded by passing them through an encoder which creates a high energy field. This field causes the card to be permanently magnetized with the card code. Magnetic stripe cards are available in low or high coercivity models.
Low Coerciviity cards require low energy to encode the card, they are also easily damaged by various magnetic sources.
High Coercivity cards require high energy to encode. They are more rugged and will not be easily damaged by magnetic sources.
Magnetic stripe readers have an exposed read head, similar to a tape recorder. They are not the best choice where dust, dirt, heavy rain or vandalism is a problem.

Wiegand

Wiegand cards are made with bits of specially treated Wiegand effect wires. The wires are embedded in the card in specific patterns. Each card is unique.
Wiegand cards are one of the best choices between price and performance. They are extremely difficult to reproduce, as special equipment and materials are required to manufacture them.
Wiegand performs well indoors and in harsh environments. Readers have no exposed or moving parts. They are weatherproof and perform well outdoors, and in high dust or corrosive environments.

Barium Ferrite

Barium Ferrite is one of the oldest technologies in access control. Barium ferrite is a magnetic material; in fact, common refrigerator magnets are made from this material. Barium ferrite is produced in thin sheets, which are embedded between the layers of a card, and then encoded by using a high energy field, similar to encoding a magnetic stripe card. Each card has a unique number.
Barium ferrite readers can usually be used indoor or outdoor. A heater is generally recommended when installing them outdoors. Barium ferrite readers are generally produced in insertion reader models only.
Barium ferrite cards are a good technology, since they are somewhat more difficult to copy than magnetic stripe. The readers are appropriate for indoor or outdoor applications, but are more delicate than Wiegand or proximity.

Proximity

Proximity readers, unlike the other technologies discussed, do not require the user to insert or swipe a card through a reader.When using proximity systems the user simply holds a card near the reader, which can read the card through "thin air."
Proximity readers are a good choice when it would otherwise be inconvenient to physically insert or swipe a card. Parking gates, record storage rooms, computer rooms, storage areas, warehouses, and prisoner entries are ideal applications for proximity. This is chiefly because of two unique properties of proximity readers. First, the user's hands are not required to gain entry, which leaves them free for other things. Second, the range of proximity readers can typically allow the card to be read from up to 1 foot away. Proximity readers are ideal when trying to present a card from a car window, when a police officer is escorting a prisoner, or when personnel are moving large bulky items into or out of storage areas or computer rooms.
Proximity readers are available in both indoor and outdoor versions, and are made in read ranges from 2 inches to 6 feet. Most can read through common building materials, so they can be embedded in the wall out of sight. Some types must be kept several inches away from metal, which will effect the* ability to read the cards.
Proximity cards contain an electrical circuit, which is activated when it is brought into the reader's field. Since these cards contain an electronic circuit, they can be damaged more easily by bending or flexing than other technology cards. Cards are made either active or passive. Active cards have a lithium battery, and therefore, a life expectancy of about 5 to 7 years. Passive cards have a passive electronics circuit, which responds when placed in the reader's field. They do not have a battery, and therefore have a very long life.

Biometrics

Biometric readers work on a property of your body. There are biometric readers which read the retina, voiceprint, fingerprint, and hand geometry of each individual employee. The hand geometry reader has received the highest level of user acceptance.
Biometric readers require each user to be logged into the system before use. Most biometric readers allow the data bundle, which identified the user, to be sent to other readers on the system, or to another building, so the user only needs to log in once. In order to reduce the time it takes to get a valid read, systems usually require entry of a PIN (personal identification number) by the user. The PIN number locates the user's template or record, and the system then compares the read to the template called from memory. If the read matches the template, entry is allowed.
Since these readers work on a property of the body, no cards are required. This makes them ideal for any application where significant problems would be incurred by cards being lost and not reported, duplicated, or given to unauthorized personnel. They provide true identification of the person and not just the card. Biometric readers are gaining wide acceptance in time and attendance applications, since personnel must be there to clock in and out. Friends can no longer "punch out" for others.
Each reader is a complete access control system by itself, or can be networked together to a personal computer for system management and reporting. This becomes even more appealing when we consider that there are no card costs for biometric readers.

Barcode

Barcode readers are sometimes used when the customer has an existing system that uses barcode and wants card compatibility, or when large populations of cards are needed at a very low cost such as at a college or university. Barcodes are similar to the codes that are scanned at the supermarket checkout, but the card is generally swiped through a reader by the user as opposed to scanning it. Typical barcodes are easily duplicated, but barcodes can be made more secure by masking them, such that they can be read by the barcode reader only. Barcode readers can be used in both indoor or outdoor applications.

Keypads

Keypads are another choice for controlling access to an area. In keypad systems a multi-digit number is entered by anyone who wishes to gain access. If the number is valid for the area at that time, the door will be released.
Keypads should not be ignored. They are a very good choice for low risk areas where we might want to keep the general public out, but where any employee would be allowed.
Keypads also allow entry only at pre-programmed times, and therefore improve control after hours. Keypads are usually the least secure, since the numbers can easily be given to others. This problem is alleviated, but not eliminated, in systems where each user is assigned a unique number, since they are responsible for the security of their privately assigned number.
Keypad systems are inexpensive, because cards do not have to be purchased.

Card and Keypad Combinations

The security of card systems can be significantly enhanced by card and keypad combinations. In these systems, a keypad number must be entered after the card is used. Both the card number and the keypad number must be valid for entry to be granted. Each card user is assigned a separate keypad number called a PIN (personal identification number). When using keypads in conjunction with cards, lost or stolen cards cannot be used to gain entry, since the keypad number would not be known.

Wiegand Output

A variety of devices on the market today provide Wiegand emulation. Keypads, proximity readers, biometric readers, and other devices change their data to emulate a standard Wiegand reader. This allows them to be wired into a system as if they were a standard Wiegand reader, which increases application flexibility, and reduces wiring to 5 conductors. Wiegand numbers can be of differing bit lengths to be compatible with different systems. The bit length represents the length of the Wiegand code; 26, 27, and 32 bit cards are popular. When using a Wiegand emulation device, it must simulate the bit length of the panel it will be wired into.

Facility Codes or Site Codes

A facility code, which is sometimes called a site code, differentiates one users card group from another. A facility code is an integral code that is programmed into the card at the time of manufacture. The additional code ensures that even if card numbers are duplicated by the manufacturer, that the cards will not operate on someone else's building who has a different facility code. Limitations inherent in the card manufacturing process result in the ability to produce a finite card population, after which codes are duplicated. Facility codes overcome this limitation adding a second code which is checked at the reader. If the facility code does not match the programmed code, entry is denied.

Access Control Cards

The cards for access control systems are usually credit card sized, and will vary in thickness. Some card technologies permit smaller cards to be used; proximity readers and Wiegand readers can use "key cards" which will fit on a key chain.
Cards can also function as photo identification, by laminating a photograph and other custom corporate artwork into the card itself or using a card that allows the user to print directly on the card using thermal sublimation printers. Access control systems today can incorporate this type of badging into a single system with a common database. In these systems, the image of each individual is stored in the computer itself, along with personal data. The badge can be modified and reissued at any time, as needed. A single database eliminates redundant data entry into separate badging and access control systems, which has been common in the past.

Understanding Access Control

To understand access control, we must understand the language of the industry. Terms like alarm inputs, relays, time zones, anti-passback, shunt, and access levels are commonly used when discussing access control systems. It is not uncommon for someone to say we will shunt the alarm on the anti-passback door during timezone 2, and trip the relay during timezone 4. But what does this mean? Let's examine the basic terminology used in today's systems. We will start with timezones.

Timezones

Timezones are used to control when things will happen. A timezone usually consists of a start time, a stop time, and selected days of the week. Rather than re-keying the entire timezone each time we want to use it, systems will generally provide the ability to use a name or a number which will represent the entire timezone.
For example: Timezone number 5 may be programmed for the warehouse crew to work from 8 AM to 12 PM every Saturday.
When programming timezones a 24 hour clock is always used; use of a 24 hour clock allows the system to differentiate between 11 AM and 11 PM. When using a 24 hour clock midnight starts at 0:00, while lunch time is 12:00. Hours are to the left of the colon (:) while minutes are to the right. Afternoon begins at 12:00 and continues to 13:00, 14:00, 15:00 etc. In some systems timezones cannot span midnight, but by linking two timezones together the system can handle events which begin one day and continue to the next.

The following chart helps to explain the time cycle:

Time Equates To
00:00 Midnight
02:00 2 AM
06:00 6 AM
12:00 12 Noon
13:00 1 PM
14:00 2 PM
19:00 7 PM
23:59 One Minute before Midnight

At midnight the clock starts at 00:00 again.

When setting up timezones, the days are just as important as the time. Typical needs include access for staff 9:00 AM to 5:00 PM Monday through Friday. Supervisors, managers, and owners may have access 24 hours a day, 7 days a week, including all holidays.
Most systems will allow holiday programming, so if a holiday occurs during a weekday, the system will allow only people designated for holidays to gain entry.
If a particular cardholder has access for an area on a normal weekday, but that day has been designated as a holiday, the user would be denied access unless his timezone includes holidays. The operation of alarms and relays may also be programmed for different operation on holidays.
Timezones may get quite detailed. For example, a user may have different access needs on different days, as in the following example:

08:30-17:00 Mon Wed Fri Standard Hours
08:30-19:00 Tue Thur Stays Late 2 Days a Week
08:00-12:00 Sat Half a day on Saturday

Different timezones may be assigned to different people for the same areas. Likewise, a single user may be allowed through some doors always, and other doors during certain times only. Lunch rooms and break areas may only be open from 11:30 to 1:30, while the lobby area may be entered at any time. A single card can be programmed for both these areas.
Timezones can be used to control other things besides access times to various area for employees. Relays can be turned on and off, alarm zones can be activated or deactivated, and doors can be unlocked, all automatically when a timezone is activated by the system clock.

Access Levels

Access levels determine where a user's card will be valid. A single name is assigned to each access level, and represents the group of doors the cardholder will be programmed for. When we assign an access level for a card, we are assigning an entire group of doors to that card. This eliminates the tedious programming of each door for every user that would otherwise be required.
Access Levels are combines with timezones to determine both where and when a cardholder can gain access.

Anti-Passback

Tailgating is when one user enters with a valid card read, and several people enter without using their cards. Anti-passback can be implemented to help alleviate this problem, by tracking whether the card is inside the secure area or outside.
When anti-passback is used, a card must first be used at a designated "in" reader, then at a designated "out" reader, before it can be used to "read in" again. In the event that the user did not read in at the in reader, and tried to read out of an area, an anti-passback violation would occur. The violation may just log the event as an alarm condition, or may not allow the door to be released. Since users who fail to use their card and walk in with other employees may get stranded or locked in, they are more likely to be sure to use their card each time they enter or exit. Readers on each side of the door are required for implementation of anti-passback.

Relays

A relay is an electronically controlled switch. Similar to a light switch on the wall being used to turn on or of 3 a light, a relay can be used to turn on or off other devices.
Relays are used to activate the electric door lock, or to activate a variety of other items such as:

Relays are located on the access control panel. Each panel will have one or more relays. Typically, one relay is used to control the electric strike. The others can be used as needed.
When a relay is activated or deactivated, the device wired to it is turned on or off. Relays can be activated or deactivated for a short, user-programmable time period from 1 second to several minutes, or even several hours. The electric door locks used on access control systems are usually turned on for 3 to 5 seconds.
Relays can be activated or deactivated by a variety of events. An alarm input, a valid card read, an egress button being pushed, or a timezone can all activate a relay. The relay will then turn on or turn off the device wired to it.

Alarm Monitoring

Access control systems typically have multiple alarm inputs. Alarm inputs are used to monitor various devices which are wired back to the panel. When a card reader is installed on a door, an alarm contact is usually installed as well. The alarm contact is used to monitor whether the door was forced open, or left open after a valid access was granted. The alarms are reported to the system operator on a display or printout.
Some of the devices that are typically monitored by access control systems are indoor motion detectors, panic alarms, various doors (doors with and without card readers), loading dock doors, temperature, windows, glass break sensors, etc.
Shunting of alarm devices which are being monitored, means to bypass or ignore the alarm for a specified period of time. Alarms can be shunted by an event or a timezone.
When an access control door is monitored with an alarm contact, the alarm contact will be shunted on a valid card read. The shunt time is user programmable; typical shunt times are 30 to 45 seconds, but may be adjusted as needed in the panel's programming.
If the access control door is monitored with an alarm contact, the alarm contact must be shunted (bypassed) every time an authorized person passes through the door. If the door is opened without the point first being shunted, an alarm will be activated.
If a valid card read shunts the alarm when going in, what about when going out?
Alarm contacts must be shunted on egress.
There are two ways to shunt an alarm when leaving. First, a card can be required to open the door from each side. This is a called read in and read out. The second method is to install a special alarm input called an egress button. Virtually every access panel has a special egress input. When activated this input will shunt the associated door alarm, and may also be used to activate the relay, which in turn unlocks the electric door lock.
Egress buttons may be activated and deactivated by timezones. This would set up valid times that the door could be exited from. If the egress button were pressed at any time other than the valid timezone, the door would remain locked or sound an alarm if opened. Car must be taken to provide effective door alarm shunting when people exit. Otherwise excessive false alarms will be reported.
The choices for egress devices are influenced by your choice of electric door locks. Some styles of electric locks keep the door locked from both sides, until a valid card read or egress request is received. Egress buttons work well with these types of locks; drop bolts and magnetic locks fall into this category.
Other locks will allow free egress by turning the door knob. Remember if the door knob is turned and the door is opened without the egress button being pressed first, a false door alarm will be received. The problem is that human nature being what it is, no-one will press the egress button when they can simply turn a knob to go out the door. Passive infrared motion detectors work well in these applications, since they will automatically trip the egress input as someone approaches the door.

Alarm Supervision

When alarms are supervised, they are constantly monitored for opens or shorts caused by faulty wiring or tampering. When a &fault is detected, a trouble report is sent to the operator.
Systems are available with and without supervised alarm inputs.

Access Control Panels

The access control panels vary depending on your application and the particular manufacturer you are working with. Every panel or device made serves as an interface to the readers and door locks. Most of these panels are interconnected by wiring in a network.

Electric Door Locks

The electric door lock keeps the door locked and secure, and releases the door when a valid card is used, or a valid egress request is received. The electric lock is an electro-mechanical device. Since it has many mechanical parts, electric locks are subject to wear and failure. Since a lock failure can defeat the entire security of a facility, a quality lock should be installed on every door.
Electric locks are available in a variety of configurations to fit virtually any door made. Lets discuss various doors that may need to be secured. There are many.
One type which is common is a wood or metal door, with either a wood or steel door frame. Some doors on schools, industrial buildings, and warehouses are outfitted with a crash bar for exit. These doors have a bar, which is about waist high and runs across the door. When depressed the bar releases the door. Other doors encountered may be clear herculite, and may or may not have a frame. Banks and retail stores, and some industrial buildings may have aluminum door frames, and aluminum framed glass doors.
Determining the proper locks for the door can be an intimidating experience. Electric locks used on access control systems include electric strikes, magnetic locks, drop bolts, and electrified locksets. With careful consideration, the proper lock can be easily specified.
Doors can be hinged on either the right or left side. Some locks may be used on either right hand or left hand doors, while others must be ordered properly handed for the door. To determine if a door is a right handed door or a left handed door, stand on the push side of the door. If the hinges are on your right, it is a right handed door. If the hinges are on the left it is a left handed door.
An electric lock which is installed at knob height on the door frame is called an electric strike. When this type of electric lock is installed, the existing lockset strike plate on the door frame is removed and the new electric strike is installed in its place. Electric strikes are installed by cutting into the door frame at the same height as the door knob. The strike chosen must be compatible with the lockset (door knob) on the door. When evaluating a lockset look to see if it is a mortise, cylindrical, or rim type, and what the latch projection is.
The latch is the part that sticks off the edge of the door, and is retracted when the knob is turned. Typical latch projections are 1/2", 5/8", or 3/4". The strike should be deep enough to allow the latch to be fully extended, without hiking the back of the strike.

Cylindrical and Mortise Locks

Cylindrical locks are common today. They can be identified by looking tat the edge of the door. Cylindrical locksets are installed in a door by boring a hole of about 1" diameter in the frame for the latch. A cover plate keeps the latch in alignment and provides a finished look.
Mortise locks can be identified by looking at the edge of the door as well. A mortise lock is installed into a mortise. A mortise is a large rectangular pocket, which is chiseled into the door itself, and is usually 3" to 4" high.
Rim strikes are installed for doors which have crash bars on them.
Door hardware comes in standard sizes. When installing a strike the existing catch on the frame will be removed and the electric strike will be installed. The existing catch is usually a standard ANSI size. Some cutting of the door frame is always required for installing electric strikes. The cutting can be minimized by choosing a strike that will fit the standard ANSI cutout for the door frame. By using a strike that matches the existing cutout on the frame, only a small cutout on the face of the door frame needs to be made. The strike can then be fitted into the existing ANSI cutout, and fastened to the existing screw holes.
Wood door frames are inherently weak. When choosing a strike for a wood frame door, look for a unit that will require a minimum cutout, and that will space the screws which fasten the strike to the frame as far away from the cutout as possible. Minimizing the size of the cutout in the frame provides the strongest installation possible.

Magnetic Locks

Magnetic locks are surface mounted and are quite easy to install. A magnetic lock, which is sometimes referred to as a mag lock, is a two piece lock consisting of an electro-magnet, and an armature plate. The electro-magnet is installed on the door frame; the armature is mounted to the door itself The lock creates a magnetic holding force of up to 1,500 pounds which hold the door shut by holding the armature to the magnet until the electric power is removed. Magnetic locks have no moving parts and are therefore very reliable.

Electric Lock Considerations

When choosing a lock for an access control system, you would almost always want to use a continuous duty model. Electric locks are available in intermittent or continuous duty models. Intermittent duty models are designed to be powered for less than 1 minute, while continuous duty models can be powered for longer than 1 minute. Virtually every access control system provides the operator with the ability to continuously unlock a door. An intermittent duty lock will burn out if energized beyond a few minutes, and therefore would not normally be used.
Locks are available in fail safe and fail secure versions. Simply stated fail safe versions are normally powered and released or unlocked when power is removed. Fail lock versions are normally locked when they are not powered, and unlock when power is applied. To look at them from another viewpoint:
Fail lock strikes, which are also known as fail secure, remain locked in a power failure condition. Fail safe strikes release the door in a power failure condition.

Fire Egress

Safety and security of the personnel in the facility are of paramount consideration when implementing an access control system. Every local code requires safe uninhibited exit from a building in the event of fire or other emergency. However, in order to provide an effective access control system, it is sometimes necessary to secure these egress points with access control card readers. When this is necessary either mechanical egress must be provided, or a fail safe strike or lock is installed on the door.
Mechanical egress systems allow the door to be released by a crash bar, or by turning the knob to open the door, which will allow the user to exit the building uninhibited during an emergency.
If securing the door will inhibit emergency egress and mechanical egress is not available on the door, then the strike, mag lock, or dropbolt is additionally tied into the building fire system which will break power to the lock whenever a fire condition is detected.
Local codes and authorities should be consulted to ensure all systems installed will be in compliance.
Certain doors on a facility may be fire rated doors. Fire rated doors are designed to stop the spread of fire throughout a building. Building codes require fire rated doors to remain locked, and to withstand certain duration of fires without burning through. Fail lock strikes are required on fire rated doors; the lock must be designated as a fire rated unit, which will withstand a sustained duration fire condition Fire rated doors can be identified by a tag on the hinge edge of the door.

Reporting Logging Printing and Interfacing with the Users

Access control systems range from simple to complex in how they provide the ability for the customer to program them and receive activity logs from them.
Some simple systems use a hand held programmer which can be taken to each individual reader on the system. Some of these systems will allow the user to retrieve or log the cardholder's entry to each door to a printer.
Other systems can be wired together in the facility, on a data communications buss. These systems will allow the operator to program any panel without leaving their office, by using a proprietary programmer that is compatible with the field panels. These systems also report valid access activity back on the communications buss to a central logging printer.
More sophisticated systems use a network of field panels wired on a communications network back to a central computer. Central computers provide excellent user interfaces for access control systems and offer the following improvements and advantages.

Advanced computer based systems can have several computers or workstations, wired together in a network. These systems will allow various system operators to perform different functions at each workstation. One operator may be handling alarms, while another would be programming additional cardholders, while a third might be running a report.
Many systems available today offer a software interface to allow events received by the access control system to be sent out to a CCTV system to call a particular camera to system monitor, when an alarm or card read is received. The software interface uses data communications, as opposed to hard wiring alarms and relays between the two systems.

Systems Architecture

Access control systems use centralized processing, distributed processing, or hybrid arrangement. The system architecture should be taken into consideration when designing an access control system, since it can have a significant effect upon operation during a catastrophic system failure.

Centralized Processing

In computer dependent processing systems, all events are gathered by the field panels, and are then sent to the computer for processing. For example if a card is presented at a reader, the reader sends the card number to the central computer or processor. The computer checks the card number against its programming and determines if that card is allowed through that door at that time. If the card is valid the computer sends a command back to the panel to release the door.
In these systems if the computer goes down, or if communications between the panel and computer is lost, the system can no longer function, to verify proper access, and to process alarms.
In computer dependent systems, the field panel checks the facility code of the card prior to sending it to the computer. When the panel can not communicate with the computer, the system will go onto a "degraded mode." When in degraded mode, the panel will verify the facility code of the card, and will let anyone in who has a valid facility code. This means that entry is granted regardless of whether that person is allowed at that door, and whether it is a valid time for the entry or not, provided the cardholder's facility code matches the system facility code.
Some centralized processing systems will prevent any access during degraded mode, while others will allow only a small pre-group of cards to gain entry during degraded mode; and some systems will provide little or no control letting virtually any cardholder go anywhere.

Distributed Processing

In distributed processing systems the database is loaded to the field panel. All decisions are made at the field panel and are passed to the computer or logging printer for storage. In these systems if communications is lost, access control continues uninhibited. Furthermore, the events can sometimes be stored in the panels, and can be sent up to the computer once communications is restored.
Due to their architecture, systems which employ distributed processing generally offer better reliability, and faster response than systems that rely on central computers for all decision making.

Determining the Correct System

Choosing the correct systems for your customer's needs is important. In order to do an effective system design, answers to the following questions are required:

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