high frequency inverter glossary of terms (m - r) - cctv by instrom ltd
Ratio between the focal length of the lens and the focal length of the standard angle lens.Indicates the magnification of the image compared to the image of the standard angle lens.Type of lens that requires manual focus.An advanced switcher that can switch signals from any input to any number or combination of outputs.Usually used in larger and more complex systems, the matrix will usually contain a series of additional advanced features.The method of transmitting signals using microwave frequency links.It is not affected by bad weather, but it is necessary to go directly to the scene.A license may be required to operate a microwave frequency system.Short term modulation-Demodulate.The modem is used to convert between analog and digital signals and then transmit and receive signals over the PSTN network.When observing the high-frequency pattern with a CCD camera, an unwanted effect appears in the video image, and the pixel pattern of the CCD camera is close to (but below) the object pattern.Concentrated recording of multiple video signals on a single video tape or hard drive.The concept of transmitting several signals over a single channel.A device that combines multiple signals into one signal.It is usually used in CCTV to describe a device that is mainly used to reuse several video signals into one video signal for recording or microwave transmission.It can also refer to the combination of multiple video signals into one optical fiber MUX in order to transmit all video signals through one optical cable.Refers to normally closed and normally open contacts.It is usually used to describe alarms in CCTV.Numerical aperture.Measure the degree of angle acceptance of light entering the fiber optic cable in cone form.It is expressed as the square root of the square difference between the core and the cladding index.National Bureau of Standards.The neutral density filter is an optical filter that has attenuated the light several times.This attenuation is equal for all wavelengths, so it does not change the color balance of the image, so the term is "neutral ".Unit of luminosity used to measure brightness.A cand is equal to a candela per square meter of the projected surface area.All circuits that work above absolute zero generate unwanted signals.Noise can not be eliminated and can only be minimized.The National Television System Commission, an American commission, sets standards for color TV sets used today in the United States, Canada, Japan and some other countries.Output.Objective.The first optical element in front of the lens.The last optical element on the back of the lens (one closer to the CCD chip ).(Also CRO from "cathode ray oscilloscope ).An electronic device that can measure the change of signal over time.Any CCTV technician must attend.Represents the Phase Alternating Line, describing the color phase change in the PAL color signal.(P/T head).A motorized device that allows the camera and lens to combine vertical and horizontal positioning.This P/T head usually uses a 24 VAC motor but also a 110 VAC.240 VAC can be ordered.A motor device that allows the camera to position horizontally.Very strong unit of light at lighting level.A phot equals 10,000 luxes.A semiconductor device in which a pn junction diode acts as a photoelectric sensor.PHOTO-Also called photoelectric effect.This refers to the phenomenon that electrons are emitted from metals exposed to light on the surface.Photon.Represents the quantum properties of light.It is considered the smallest unit of light.Light intensity range from 105 lux to nearly 10 lux2 lux, can be detected by the human eye.A lens with a fixed focal length for viewing through a very small aperture for discrete monitoring of the situation.The lens usually does not have focus control, but provides an option for Iris function.From the image element.Usually refers to the unit picture unit of CCD chip.It consists of a photo sensor and its associated control door.The thermal ion vacuum tube developed by Philips uses lead oxide photoelectric layer.It represents the ultimate imaging device before the introduction of the CCD chip.An optical filter that transmits light in only one direction (perpendicular to the optical path) in the range of 360 °.The effect is this, it can eliminate some unwanted bright areas or reflections, such as when looking through the glass windows.In photography, polarising filters are often used to darken the blue sky.Simple old phone serviceUniversal telephone service in the world today.Also known as the PSTN.The function of the pan and tilt unit, including the zoom lens, in which certain viewing positions can be stored in system memory (usually in the PTZ site driver) and, when required, recall by programming or manual recall when an alarm is triggered.An optical term that refers to one of the two points each lens has along the optical axis.When measuring the focal length of the lens, the principle point close to the imaging device (in our case the CCD chip) is used as a reference point.The public switched telephone network usually refers to the business of "ordinary old telephone.Also called basin.(PTZ field receiver or Decoder ).An electronic device, usually part of a video matrix switcher, that receives control signals digitally encoded in order to operate translation, tilt, zoom, and focus functions.(Also split screen unit ).A device that displays parts or multiple images at the same time on a single display.It usually refers to the display of four quadrants.Redundant array of independent disks.This is a technology that connects multiple hard drives to a large-capacity storage device, which can be used, among other things, for digital recording of video images.Random memory accessAn electronic chip, often referred to as a "memory", that holds digital information when powered on.Its capacity is in thousands of words.Describes the terms of the camera with free-running horizontal sync, rather than the 2:1 staggered type with Synchronous Locking, so the two fields in the frame are exactly staggered together.Used to control the transmission and reception of signals from remote devices such as pan and tilt devices, lens functions, cleaning and wiping controls.Name of former EIA Association.Some of the old video test charts have the name of the "RETMA Chart.RF signals belonging to the region up to 300 GHz.RG-A video coaxial cable with a impedance of 75 ohms and a much thicker diameter than the popular RG-59 (about 12mm ).With RG-A longer distance can be achieved (at least twice that of RG)59), but it is more expensive and difficult to work with it.RG-Therefore, coaxial cables designed with a 50 ohm impedance are not suitable for CCTV.Very similar to RG-59, only a little thinner.RG-A coaxial cable that is most common in medium and small CCTV systems.Its design impedance is 75 ohms.Its outer diameter is about 6mm, and there is a good compromise between the achievable maximum distance (monochrome signal up to 300 m, color signal up to 250 m) and good transmission.Abbreviation of root mean square.All AC voltages are measured with a multimeter that displays the RMS value of the signal (not the peak value.For sine wave signals such as power supply, the RMS value happens to be 1.41 times below the peak (square root of 2 ).Read-only memory.An electronic chip containing digital information that does not disappear when the power is off.RS-A digital communication format that requires only two wires.It is also called serial data communication.The RS-The 232 standard defines a scheme for asynchronous communication, but it does not define how data should be represented in bits, I .E.It does not define the entire message format and protocol.It is often used for communication between CCTV keyboards and matrix switches, or between matrix switches and PTZ site drivers.Advantages of RS-Compared to other wires, the 232 wire is very simple and only two wires are used.RS-This is an advanced digital communication format compared to RS-232.The basic difference is that four wires are needed instead of two because communication is not singleEnd with RS232, but there are differences.In short, the signal sent is "read" at the receiving end because there is no difference between the two wires that are public grounded.So if there is noise along the line, it will be canceled.The RS-The 422 can drive lines of more than one kilometer in length and distribute data to up to 10 receivers.RS-This is an advanced digital communication format compared to RS-422.The main improvement is the number of receivers that can be driven in this format, which is up to 32.