Glossary Of Terms M - R - CCTV
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Glossary of CCTV Terms (M - R)
Overview
This glossary provides a clear and concise guide to key CCTV terms from M to R, enhancing your understanding of surveillance technology.
Terms
Magnification Ratio:
This indicates how much an image is magnified compared to a standard angle lens. It's the ratio between a lens's focal length and that of a standard angle lens.
Manual Iris:
A lens type that requires manual focusing.
Matrix Switcher:
An advanced switcher allowing any input signal to be connected to multiple outputs, typically used in extensive and complex systems with additional advanced features.
Microwave Transmission:
A method using microwave frequencies for signal transmission, unaffected by adverse weather but requiring direct line of sight. Licensing may be required.
Modem:
Short for Modulate-Demodulate, it converts analogue and digital signals for transmission over PSTN networks.
Moiré Pattern:
An unwanted video effect from high-frequency patterns captured by a CCD camera with a similar pixel pattern.
Multiplex Video Recording:
The process of recording multiple video signals on a single videotape or hard disk.
Multiplex:
Transmitting multiple signals over one channel.
Multiplexer:
A device that combines several signals into one, commonly used in CCTV to multiplex video signals for recording or transmission.
N/C and N/O Alarms:
Describes Normally Closed and Normally Opened contacts, typical in CCTV alarm systems.
NA (Numerical Aperture):
Measures the angular light acceptance into a fibre optics cable, using the core and cladding indices.
NBS:
National Bureau of Standards (USA).
ND Filters:
Neutral Density filters that uniformly attenuate light without altering color balance.
Nit:
A luminance measurement unit, equal to one candela per square meter.
Noise:
Unwanted electrical signals present in circuits, which can be minimized but not eliminated.
NTSC:
National Television System Committee, standardizing color television in the USA, Canada, and Japan.
O/P (Output):
Refers to the objective lens element at the front.
Ocular:
The optical element at the back of a lens, closest to the CCD chip.
Oscilloscope (CRO):
A device measuring signal changes over time, essential for CCTV technicians.
PAL:
Phase Alternating Line, describing color phase changes in PAL signals.
Pan and Tilt Head (P/T Head):
A motorized unit for vertical and horizontal camera positioning, available in various voltage options.
Pan Unit:
Allows horizontal camera positioning.
Phot:
A unit measuring strong illumination levels, equivalent to 10,000 lux.
Photodiode:
A semiconductor device acting as a photo-sensor.
Photo-Effect:
The phenomenon where light exposure ejects electrons from a metal surface.
Photopic Vision:
The range of light intensities detectable by the human eye, from 10⁵ lux to nearly 10⁻² lux.
Pinhole Lens:
A fixed focal length lens used for discrete surveillance, offering minimal aperture viewing.
Pixel:
Short for picture element, refers to a CCD chip's picture cell unit.
Plumbicon:
A thermionic vacuum tube developed by Philips, a prominent imaging device before CCD chips.
Polarising Filter:
Transmits light in one direction, used to eliminate reflections and unwanted brightness.
POTS (Plain Old Telephone Service):
Refers to the traditional telephone service, also known as PSTN.
Preset Positioning:
A function allowing specific camera positions to be saved and recalled, often used in PTZ systems.
Principle Point:
A lens's reference point along the optical axis for measuring focal length.
PSTN:
Public Switched Telephone Network, synonymous with POTS.
PTZ Site Driver:
A device controlling pan, tilt, zoom, and focus functions, often part of a video matrix switcher.
Quad Compressor:
A unit displaying multiple images simultaneously on a single monitor, typically in quadrants.
RAID (Redundant Arrays of Independent Disks):
A technology connecting multiple hard drives into one storage device for digital video recording.
RAM (Random Access Memory):
Electronic memory storing digital information while powered, measured in kilobytes.
Random Interlace:
Describes a camera with free-running horizontal sync, unlike 2:1 interlace types.
Remote Control:
Signal transmission and reception for controlling remote devices like pan and tilt units.
RETMA:
Former name for the EIA association, seen on older video test charts.
RF Signal:
Radio frequency signals up to 300 GHz.
RG-11:
A coaxial cable with 75 Ohms impedance, thicker than RG-59 for longer distances.
RG-58:
A 50 Ohms coaxial cable, unsuitable for CCTV.
RG-59:
A common 75 Ohms coaxial cable in small to medium CCTV systems, balancing distance and transmission quality.
RMS (Root Mean Square):
Measures AC voltages with multimeters showing the RMS value, important in electrical measurements.
ROM (Read Only Memory):
Chip storing non-volatile digital information.
RS-232:
A simple digital communication format using two wires, often in CCTV for device communication.
RS-422:
An advanced digital format using four wires for differential communication, minimizing noise interference.
RS-485:
Further advancement on RS-422, supporting up to 32 receivers.
Incorporating these terms can greatly enhance your understanding and efficiency when working with CCTV systems.
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