scope:

This specification relates to design requirements for a miniature tractive armature slow release line relay of the plug-in type for use in signalling circuits energised by a battery or rectified ac.c supply. It is suitable for use in lamp circuits carrying a nominal current between 1.0 amp and 2.0 amps. It can be used in circuits carrying higher currents by the provision of a suitable shunt resistance.

The design is based on the requirements that when used with multiple unit signals 16 watt or 24 watt lamps the relay shall remain in the operated position long enough to cover the contact transit time of the signal control relay.