AV/IT Glossary—27 Days of #AVabc—O



OLED—A light-emitting diode containing thin flexible sheets of an organic electroluminescent material, used for visual displays.


OCR—Optical Character Reader or Optical Character Recognition. Hardware and software that reads characters as images and converts them into text to be used in a computer.

Octave—A doubling or halving of a frequency. For example, 200 Hz is one octave higher than 100 Hz; 50 Hz is one octave lower.

Off-line—A cost-effective preliminary stage of video editing, using low-grade copies of the edited material mainly for control and edit-design purposes.

Ohm—The unit of electrical resistance, transmitting a current of 1 amp when subjected to a potential difference of 1 volt. Represented by W or Z.

Ohm’s Law—Defines the relationship between current, voltage, and resistance in an electrical circuit as proportional to applied voltage and inversely proportional to resistance. The formula is I=V/R. I-current (in amps), V= voltage (in volts), R = Resistance (in Ohms).

Oirt—An obsolete eastern European broadcasters' union, which merged with the EBU in 1993. The name was also used to describe the broadcasting system in the Eastern Block - a modified SECAM system.

Omni-Directional—Describes the shape of the area for microphones that have equal sensitivity to sound from nearly all directions.

On-Axis—The center point of a screen, perpendicular to the viewing area for a displayed image. This is considered to be the best location for viewing.

On-Line—Actual video editing, using high quality materials usually based on decisions made during the Off-Line stage.

Operating System (OS)—Platform; Enables software applications to communicate with the CPU.

OPEX—Operating Expense. An ongoing cost for running a product, business, or system.

Optical Ethernet—An optical connection for delivering Ethernet packets. Ethernet signals have been traditionally interfaced on twisted pair cable. Optical Ethernet connections are used to preserve quality delivering the same signal over a greater distance or security concerns.

Optical Link—A single fiber optic signal path or point-to-point fiber optic connection between a transmitter and receiver, including connectors, fiber, splices, and other fiber optic components in the path.

Optical Loss Test Set-OLTS—Test equipment for singlemode or multimode optical fiber comprising a light source and a power meter, used to measure optical signal loss along the fiber and any connectors in between.

Optical Return Loss-ORT—A measure, in dB, of the amount of optical power reflected within a fiber optic pathway due to the fiber and optical components.

Optical Time Domain Reflectometer-OTDR—An instrument in fiber optics used to measure backscattered light in the detection of defects along a span of optical fiber.

Oscilloscope—A test device that allows measurement of electronic signals by displaying the waveform on a CRT screen.

OSI Model Open System Interconnection Reference Model—OSI Reference Model is a definition for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection (OSI) initiative. The OSI model divides the network architecture into seven layers starting from the bottom up: Physical, Data Link, Network, Transport, Session, Presentation and Application Layers.

Out of Order Packet—In computer networking, the delivery of data packets in a different order from which they were sent. Video decoders must account for out of order packets which may be experienced.

Output Power—In fiber optics, this is the radiant power, expressed in watts.

Outside Plant-OSP—In a telecommunications network, this is the portion that is situated mainly outdoors. This includes patch panels, closure, pedestals, cabling, poles, towers, repeaters, and other equipment.

Overbooking—In the telecommunications industry, overbooking -- such as in the frame relay world -- means that a telephone company has sold access to too many customers which basically flood the telephone company’s lines, resulting in an inability for some customers to use what they purchased.

Overcurrent—Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, a short circuit, or a ground fault.

Overfilled Launch Condition-OFL—In fiber optics, a condition where the incoming light has a spot size and numerical aperture–NA larger than acceptable by the fiber. Typically associated with LED transmission and multimode cable.

Overhead—Any data which is transferred on a communication link which is in addition to the content or data that is delivered. In IP networks, overhead includes: addressing, control, routing, redundant, errorchecking and error concealment data.

Overhead Projector—A device which produces an image on a screen by transmitting light through transparent acetate placed on the stage of the projector.

Overlay—Keyed insertion of one image into another. Overlay is used, for example, to super-impose computer generated text on a video image for titling purposes. The overlay procedure requires genlocked* sources for proper operation. In the computer field, overlay files are accessory files containing mainly graphics information, following or within computer programs.

Oversampling—When a signal is digitally sampled at frequencies much higher than the NYQUIST* frequency. When this method is used, filtering the signals is easier and less expensive, although sampling at higher frequencies is more problematic.

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