The Collaborative International Dictionary
Block signal \Block signal\ (Railroads) One of the danger signals or safety signals which guide the movement of trains in a block system. The signal is often so coupled with a switch that act of opening or closing the switch operates the signal also.
Usage examples of "block signal".
When, far up the track, the block signal snapped from red to green and the long, stabbing probe of the headlight sheered the bend and blared on the station, men looked at their watches and said, On time.
When, far up the track, the block signal snapped from red to green and the long, stabbing probe of the headlight sheered the bend and blared on the station, men looked at their watches and said, “.
And then, after a day and a night of looting in Brooklyn, the motorman of a rush-hour Brooklyn subway express, slowing to a block signal in a tube under the river, saw the phantom, impossible apparition of the Mole lying across the tunnel.