(under subclass 479) Subject matter having semaphores which are operated in the upper quadrant and moved upward instead of downward when passing from horizontal to vertical position, so that deposits of ice on the arm will increase rather than decrease the tendency to assume the stop or danger position. They are not usually provided with counterweights.
(1) Note. Pivoted-arm signals, not strictly semaphores within the definition of subclass 479, are here included, provided they work in the upper quadrant.
