Siemens TFT - Manual (Page 204)

Glossary
16-2 © Siemens Building Technologies Group
16
Average Video Signal
Represents the average light level of the whole picture used to open
or close the automatic iris in the lens.
AVG
Alphanumeric Video Generator is a device for providing additional
information, normally superimposed on the picture being displayed.
This can range from one or two characters to full screen alphanu-
meric text. Such generators use the incoming video signal sync
pulses as a reference point for the text insertion position, which
means if the video signal is of poor quality, the text will also be of
poor quality.
Backlight compensation
Special feature of video cameras. Prevents the effect that everything
appears dark in front of a brigt object (e.g. a window).
Back Focus
The back focus is a procedure of fine mechanical adjustment in the
camera, which moves the CCD or the lens mount to compensate for
different back focal lengths of different lenses.
Backlash
An error present in a pan and tilt head due to the play in the mechan-
ical components like gears, pulleys etc. This results in the Pan Tilt
head not stopping instantaneously. This error is critical in preset PTZ
cameras and is measured in degrees.
Back Porch
The back porch is the portion of a video signal that occurs during
blanking from the end of the horizontal sync to the beginning of
active video. It is also the blanking signal portion that lies between
the trailing edge of a horizontal sync pulse and the trailing edge of
the corresponding blanking pulse. The colour burst is located on the
back porch.
Balanced Signal
In CCTV this refers to the transmission of a video signal through a
twisted pair cable. It is called balanced because the signal travels
through both cables, using opposing polarities to help reduce any
losses due to interference.
Balun
A balun is a device used to match or transform an unbalanced coax-
ial cable to a balanced twisted pair system.
Bandwidth
Is the range of frequencies which pass through an electronic amplify-
ing, processing or transmission equipment without attenuation or
loss.
Barrel Distortion
Is a distortion in the monitor due to non uniform scanning which
causes the image to bulge outward like a barrel.
Baud
The term baud is used to express the data exchange rate, typically
the baud settings of two devices must match if the devices are to
communicate with one another.
Beam Angle
Is the angular beam width of a conical beam of light and is measured
in degrees.
Bifurcator
An adapter used to split a loose tube containing two optical fibres
into two single fibre cables.
B-ISDN
Broadband Integrated Services Digital Network. An improved ISDN
composed of an intelligent combination of more ISDN channels into
one that can transmit more data per second.
Bitmap
A bitmap is a pixel by pixel description of an image each pixel is a
separate element.
BlackBurst
A composite colour video signal. The signal has composite sync, ref-
erence burst and a black video signal, which is usually at a level of
7.5 (50mV) above the blanking level.
Black Level
It electronically represents the black part of an image corresponding
to approximately 0.3 volts.
Blanking Pulse
Is a black pulse added during the fly back period to make the video
signal invisible on the screen.
BNC Connector
Is a type of connector used to interconnect two coaxial cables or con-
nect a cable with other CCTV components.
Bridging Switcher
Is a type of sequential switcher which has two outputs. The sequenc-
ing output sequences all the camera inputs whereas the other out-
put is a spot output where any camera can be called up for extended
viewing.
Brightness
Represents the intensity of illumination of the reproduced picture.
Brightness Control
Is a control in the monitor which does not change the amplitude of
the video signal but increases or decreases the illumination of the
phosphors on the screen.
Broadcasting Camera
Is a high quality camera using three CCD chips. It is used extensively
in the Broa
DC asting professional industry.
C-mount
Is a lens mount with 17.526mm back flange. The back flange is the
distance between the lens mounting surface and the CCD chip. Cam-
eras with CS-mount need a special adapter ring to be used with C-
mounted lenses (supplied with every camera).