Data Acquisition

NTSCNull modemNumber of channelsNyquist sampling theoremOCROLUTOn-board memoryOptical isolationOROSIOutputOverlayPacketNational Television System Committee (USA). Atelevision standard specifying 525 lines and 60fields per second.A device that connects two DTE devices directlyby emulating the physical connections of a DCEdevice.This is the number of input lines a board cansample. Single-ended inputs share the sameground connection, while differential inputs haveindividual two-wire inputs for each incomingsignal, allowing greater accuracy and signalisolation. See also multiplexer.In order to recover all the information about aspecified signal, it must be sampled at least attwice the maximum frequency component of thespecified signal.Optical character recognition, optical characterreader.Output look-up table.Incoming data is stored in on-board memorybefore being dumped into the PC’s memory. On ahigh-speed board, data is acquired at a muchhigher rate than can be written into PC memory,so it is stored in the on-board buffer memory.A means of connecting two networks withoutelectrical continuity; uses optoelectronictransmitters and receivers.Outside radius.Open systems interconnection. A set of definedprotocol layers with a standardized interface thatallows equipment from different manufacturers tobe connected.An analog or digital output control type signalfrom the PC to the external ‘real world’.One video signal superimposed on another, as inthe case of computer-generated text over a videopicture.A group of bits (including data and call controlsignals) transmitted as a whole on a packetswitching network. Usually smaller than atransmission block.