| 释义 |
ˈstep-down, a. and n.
[f. vbl. phr. to step down: see step v. 22.]
A. attrib. or as adj.
1. In sense 22 c of the vb.: causing or pertaining to a reduction in voltage or some other quantity.
1893Sloane Electr. Dict., Step-down adj...applied to a converter or transformer in the alternating current distribution, indicating that it lowers potential difference and increases current from the secondary. 1929Exper. Wireless VI. 307/2 This reduces the step down ratio required in the potentiometer. 1947R. Lee Electronic Transformers & Circuits vi. 172 Driver transformers are usually step-down because the grid potentials are relatively low. 1959Motor Man. (ed. 36) 95 It has a stepdown gear which reduces the speed of the propeller shaft in a ratio which is usually between 5 to 1 and 4 to 1. 1961Wall St. Jrnl. (Eastern ed.) 14 Nov. 10 (Advt.), With Con Edison's step-down rates, the more electricity you use, the less it costs per kilowatt-hour. 1981Daily Tel. 22 July 12/6 For really rough going there is a 1·96:1 step-down ratio for four-wheel-drive.
2. In sense 22 a of the vb. Esp. from or in which one steps to a lower level. Chiefly U.S.
1949Newsweek 28 Nov. 56 (caption) Hudson enters lower-priced field with smaller version of step-down car. 1954Sun (Baltimore) 8 Mar. 20/1 Dr. Clifford M. Witcher..calls his device a ‘step-down detector’. When the user approaches a curb, a flight of steps or the edge of a sub⁓way platform, the detector buzzes a warning. 1966A. R. Bellamy in Biochim. & Biophys. Acta CXXIII. 102 (title) RNA synthesis in exponentially growing tobacco cells subjected to a step-down nutritional shift. 1976Billings (Montana) Gaz. 27 June 5-d/4 (Advt.), Three bedrooms, step-down living room, and main floor family room with fireplace.
B. n.
1. A reduction or decrease.
1922[see regenerative a. (and n.) 2 b]. 1962A. Nisbett Technique Sound Studio ix. 165 The result is a sudden step-down in volume and quality just before the second signal appears on the tape.
2. The act of stepping down or withdrawing from a position.
1973Guardian 7 June 2/4 In a cleverly disguised step⁓down from the position that these controversial logs would never be released, Mr Nixon's spokesman said today that..the documents would now be turned over. |