| 释义 |
line standard
[line n.2]
a. Metrology. A standard of length in the form of a metal bar on which are engraved two lines, the distance between which (under specified conditions) is the standard length.
1888Encycl. Brit. XXIV. 478/1 Standards of length are of two types, the defining points being either at a certain part of two parallel lines engraven in one plane (a line-standard), or else points on two parallel surfaces, which can only be observed by contact (an end-standard). 1906Hallock & Wade Outl. Evolution of Weights & Measures x. 223 The line standard, of course, can be used with a microscope with cross-hairs, or a micrometer microscope, much more readily than an end standard. 1966Kaye & Laby Tables Physical & Chem. Constants (ed. 13) 7 The yard equal to 0·9144 metre supersedes the definition in terms of the former imperial standard yard, a bronze line-standard constructed in 1845. 1967A. J. T. Scarr Metrology & Precision Engin. v. 67 The calibration of a line standard is determined by comparison with a master scale.
b. Television. The number of lines constituting a complete picture.
1959C. Daniel in Rep. Comm. Broadcasting 1960 (1962) 340 in Parl. Papers 1961–2 (Cmnd. 1753) IX. 259 We understand that most of the rest of Europe are likely to adopt..a line standard of 625 lines. 1973Newnes Colour Television Servicing Manual I. i. 2/2 The degaussing action takes place automatically when there is a change in the line standard during push-button selection. |