. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . AUTOMATIC. PROCEED. ONE BLOCKAHEAD CLEAR. NO RED LIGHTS. drilling movements. At night three redlights show in a vertical line when allthe routes are blocked. When one of tharoutes is set up the light for that routechanges from red to green or yellow ac-cording to whether two or one blockahead is unoccupied. The lights of tlie May, 1909. RAILWAY AND LOCOMOTIVE ENGINEERING 191 other routes not to be taken by the tramshow rci. In the application of this principle tothe automatic system, one uppe
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . AUTOMATIC. PROCEED. ONE BLOCKAHEAD CLEAR. NO RED LIGHTS. drilling movements. At night three redlights show in a vertical line when allthe routes are blocked. When one of tharoutes is set up the light for that routechanges from red to green or yellow ac-cording to whether two or one blockahead is unoccupied. The lights of tlie May, 1909. RAILWAY AND LOCOMOTIVE ENGINEERING 191 other routes not to be taken by the tramshow rci. In the application of this principle tothe automatic system, one upper quadrantthree-position signal is used. Accordingas green, yellow or red appears the en-ginemen know that they have in front ;if CRtEN RED. INTERLOCKING, PROCEED, HIGH SPEED ROUTE CLEAR. ONE GREEN AND ONE RED. them, two, one, or no blocks clear. Thereis, however, a permanent red light dis-played lower down on this post. Thislight is not set exactly below the upperlight, but slightly to one side, thus givinga diagonal line for the centers of thalights. This indicates that the signal soequipped is an automatic one. The presenceof the permanent red light is for the pur-pose of recognizing the signal if the upperlight had gone out. With green lightabove and permanent red below, the sig-nal would indicate two blocks ahead yellow above and permanent redbelow, one block ahead would be reds would call for a stop, as inthe interlocking system, and where pro-ceed is indicated the permanent redmodified by the presence of a green oryellow light above it would still main-tain the interlocking principle where thepermission to proceed is given on thehigh-speed route by the change of theupper light. If the upper ligl
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