| 单词 | lock and block signalling | 
| 释义 | > as lemmaslock and block signalling   lock and block  n. a system of railway signalling in which a train is prevented, by means of a locked signal, from entering a section of line occupied by another train; also attributive, as  lock and block system,  lock and block signalling, etc.; cf. block system n. at block n. 19c. ΘΚΠ society > travel > rail travel > railway system or organization > 			[noun]		 > types of signal system block system1864 lock and block1872 signalling1873 1872    Scotsman 7 Nov. 3/2  				Captain Tyler considers the adoption of the lock and block systems essential only on certain classes of railways. 1894    N.Y. Times 25 June 4/4  				Mr. O'Donnell favors a combination of ‘lock and block’ which will make it impossible for the outside signals to be lowered excepting when the line is clear. 1905    Westm. Gaz. 12 Jan. 7/2  				The failure was partly due to faulty line circuits of the lock and block instruments. 1956    Railway Mag. Nov. 748/1  				The Sykes lock-and-block, although old fashioned,..has a long record of reliable service in the operation of dense traffic. 1978    G. M. Kichenside  & A. Williams Brit. Railway Signalling 		(ed. 4)	 iv. 39  				On some lines where lock-and-block signalling is used, the signal post carries a white diamond-shaped plate..indicating to the crew that the signal is exempt from rule K3. 2003    M. C. Duffy Electric Railways 1880–1990 i. 8  				Lock and block was developed using mechanical and electromechanical locking. < as lemmas  | 
	
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