Improvements in or relating to alarm-devices, more particularly for air raid alarm

Abstract

Abstract 488,442. Electric signalling systems. BUNZL, E. Feb. 22, 1937, No. 5320. Convention date, Feb. 22, 1936. [Class 40 (i)] Alarm bells or lamps connected to lighting mains are switched on by altering the strength or frequency of the current in the mains. A relay or the like connected to the mains responds to the mains variation and when operated connects the alarm device to the mains. The Specification as open to inspection under Sect. 91 comprises also the operation of the alarm by interrupting the current for a certain length of time or by superposing a current of different frequency on the mains and the switching in of emergency illumination with the alarm. This subject-matter does not appear in the Specification as accepted.

Inventors

No inventors recorded.

Bibliographic Details