Section 2(1)(d) in The Bangalore Metro Railway (Opening of Public Carriage for Passengers) Rules, 2011
(d)"automatic block system" means a system of train working wherein section between two stop signals is divided into several sub-sections or blocks by providing series of signals, the aspect of which is automatically activated by the conditions of the block beyond the signal and the movement in automatic signaling territory is governed by the aspect of signals and train is allowed to enter automatic block section at authorised speed for various aspects of automatic signals;