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term effect, and should not be confused with image retention, image burn, or sticking.
L L-band frequency band of approximately 1–2 GHz. L-L
See line to line fault.
label a tag in a programming language (usually assembly language, also legal in C) that marks an instruction or statement as a possible target for a jump or branch. labeling (1) the computational problem of assigning labels consistently to objects or object components (segments) appearing in an image. (2) a technique by which each pixel within a distinct segment is marked as belonging to that segment. One way to label an image involves appending to each pixel of an image the label number or index of its segment. Another way is to specify the closed contour of each segment and to use a contour filling technique to label each pixel within a contour. ladder diagram (1) the connection of the coils and contacts used in a control circuit shown one line after the other that looks like a ladder. (2) a visual language for specifying the Boolean expressions, which are the core of the control law of PLC. laddertron a microwave vacuum tube oscillator with a slow-wave structure coupled to a single-cavity resonator. lag the inability of an imaging tube to respond to instantaneous changes in light. For measurement purposes, lag has two components: rise lag is the response time from dark to light, whereas decay lag is the response time from light to dark. Lag is a very short-
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lag circuit a simple passive electronic circuit designed to add a dominant pole to compensate the performance of a given system. A lag circuit is generally used to make a system more stable by reducing its high-frequency gain and/or to improve its position, velocity, or acceleration error by increasing the low frequency gain. A nondominant zero is included in the lag circuit to prevent undue destabiliz