BS 764:1990

This British Standard specifies d.c. and single-phase a.c. automatic double-pole change-over contactors for low voltages up to 250 V employed in conjunction with storage batteries or other alternative source of supply, to provide a means of automatically changing the current supplied to safety lights from the normal source to the alternative source when the normal source fails, and of reconnecting the safety lights to the normal source when this source is restored.

This standard does not apply to three-phase a.c. automatic change-over contactors.

NOTE 1 Appendix B lists information to be supplied to the manufacturer with the enquiry and/or order.

NOTE 2 The titles of the publications referred to in this standard are listed on the inside back cover.

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.