BR934A Sep1971

This specification relates to design requirements for miniature tractive armature D.C slow release neutral line relays of the plug-in type for use in railway signalling circuits, irrespective of the presence in the circuit of alternating current at industrial frequency. The design is based on the requirement that the delay is sufficient to cover the changeover time of an A.C immunised neutral line relay manufactured in accordance with B.R. Specification No. 931A.