Fail Locked (Fail
Secure) |
Locking device requiring current to unlock. |
Fail Unlocked (Fail
Safe) |
Locking device requiring current to lock. |
| Fast Ethernet |
Generally refers to 100BASE-T and 100BASE-FX but may also include 100VG. |
| Field |
One half of a frame, consisting of either the odd or the even numbered lines, 50 fields are transmitted every second. |
| Field of View |
The view achieved with a particular lens; varies with the focal length. |
| File |
The orderly arrangement of data or information. |
| Firewall |
A network node set up as a boundary to prevent unauthorised traffic from one segment to cross over to another. Firewalls are used to improve network traffic, as well as for security purposes. |
| Flash memory |
A memory chip that holds its content without power but must be erased in fixed blocks rather than single bytes. Block sizes typically range from 512 bytes up to 256KB. |
| Focal Length |
Of a lens, the distance in millimetres, between its secondary principal point and its focal point. The higher the number the greater the magnification and the less the field of view. |
| Focal Point |
The point on the axis of a lens to which parallel rays of light will cover. |
| Format |
How the computer arranges the information onto disk. Can also apply to printers. |
| Frame |
One complete TV picture made up of approximately 625 lines. 25 frames are transmitted every second. |
| Frame Relay |
Packet-switched network similar to X.25 but with end-to-end error-checking and high-speed transmission rates. |
| Frame Store |
Digital information store capable of holding a complete frame of video information. |
| Frame Transfer CCD |
Type of CCD chip which consists of vertical charge transfer channels placed side by side. During vertical blanking, the charge generated in the light sensitive imaging area is rapidly transferred into a shielded storage area. During the horizontal blanking, this charge is shifted down a line at a time into a horizontal shift register where it is clocked out during each line period to form the video signal. |
| Full Picture Update |
The technology which enables a transmission system to update a high quality full picture on each picture refresh at very fast speeds. |
