BS 764 90th Edition, May 31, 1990
Specification for Automatic Change-Over Contactors for Emergency Lighting Systems
Includes all amendments and changes through Reaffirmation Notice , December 1, 2012
Published By:British Standards Institution (BSI)
Design and performance requirements for d.c. and single-phase a.c. double-pole change-over contactors for low-voltages up to 250 volts and a range of standard current ratings, which are used to provide the automatic transfer of current supplied to safety lights from the normal source to an alternative source when the normal source fails; reconnection is automatic when the normal supply conditions are restored.