BELL No. 40

D.C. Trembler bell used on fire alarm systems.

Bell 40A - Twin 50 ohm coils, 2-10 volts - used  on London F.B. systems.
Bell 40B - Twin 250 ohm coils, 10-50 volts - used in PO buildings.

Uses Bell Gong No. 21 (4.5in diameter x 3.1in - Church style)

GPO Engineering Instructions on Fire Systems

Diagram N640

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Last revised: January 26, 2016