FFL
Fixed Focal Length Lens
Fiber-Optic Cable
One of the video transmission ways, being used for a long distance transmission up to miles.
Field
One video frame is composed of two fields; one field consists of the odd numbered lines in the frame and the other field consists of the even numbered lines.
Field Frequency
The number of fields per second.
Field Of View
FOV. The width, height or diameter of a scene to be monitored. Usually determined by the focal length of a lens, the sensor format and the distance to the objects.
Firewall
A set of programs that protects the resources of a private network from outside users.
FL
Focal Length. The distance from the center of a lens (or, the secondary principal point, if it has) to the focal point (sensor). The longer the focal length, the narrower is the angle of view.
Flange-back Adjusting Ring
Some models of CCTV cameras have built-in Flange-back Adjusting Ring, which adjusts the back-focal distance or picture focus. A C-Ring (5mm spacer ring) is not required when a C-Mount lens is to be mounted to a camera that has built-in Flange-back Adjusting Ring.
Flash Memory
Or flash RAM (Random Access Memory). A type of constantly powered nonvolatile memory that can be erased and reprogrammed in units of memory called blocks.
f-number (f-stop)
Optical or lens speed. Smaller f-number means faster lens.
Focal Length
The distance from the center of a lens (or, the secondary principal point, if it has) to the focal point (sensor). The longer the focal length, the narrower is the angle of view.
FOV
Field of View. The width, height or diameter of a scene to be monitored. Usually determined by the focal length of a lens, the sensor format and the distance to the objects.
Frame
A whole video image; is composed of two interlaced fields. A CCD chip produces 30 frames per second at NTSC system and 25 frames at PAL.
Frame Frequency
The number of frames per second. The frame frequency is half the field frequency.
FTP
File Transfer Protocol. A way to exchange files between computers on the Internet
Facility Code
Coded data in access control cards that identifies the location of the access control system.
Fail-Safe Door
A fail-safe door is one that if the power should fail at that door, the door will automatically unlock allowing exit and entrance. A fail-safe door ensures people will be able to exit a secure area through that door in the case of an emergency.
Fail-Safe Lockset
A lockset that is normally locked when the power is ON, and automatically unlocks when the power fails. See Fail-Safe Door.
Fail-Secure Door
A fail-secure door is one that if the power should fail at that door, the door will automatically lock and not allow entrance, but will continue to allow exit. A fail-secure door ensures a secure area remains secure regardless of the situation.
Fail-Secure Lockset
A lockset that is normally unlocked when the power is ON, and automatically locks when the power fails. See Fail-Secure Door.
False Alarm
An alarm signal generated without an existing alarm condition.
Fingerprint Pattern Area
The identifying characteristics of a fingerprint, consisting of the arches, loops, and whorls in the fingerprint.
Fingerprint Reader
A biometric reader that identifies a person based on the person's fingerprint pattern.
