(under subclass 22) Systems in which the signal clearing operations require the cooperation of the operators at each end of the block and also the absence of trains from the block, which when present, by electrical means, render it impossible to clear the signals.
SEE OR SEARCH THIS CLASS, SUBCLASS:
26, and 106, for manually-controlled block signaling systems of the lock and block type.
131+, and the subclasses specified in the Notes thereto, for details of locking and interlocking, and switching, signaling, and similar systems.
