Improvements in or relating to distant control electric apparatus for signalling from a central station over the supply main

Abstract

Abstract 521,582. Electric signalling systems. VALVASSORI, V. March 7, 1939, No. 7416. [Class 40 (i)] A receiver for an air raid alarm &c. signals over the supply mains comprising current cut-off for a predetermined time, consists of a bimetallic strip 1 heated by coil 5 so that it takes up the extreme right-hand dotted line position where normally it intermittently makes and breaks the heating circuit at 10. The strip carries a pivoted member having insulating and conducting portions 4, 3 so that when the current is originally switched on, the strip bends and the insulating portion engages a conducting rack 7 as at 3a. When the current is switched off, the strip straightens and the pivoted member runs back along the rack with the insulating portion in engagement therewith as at 3c, but if current is switched on before the member leaves the rack, the strip bends and jams the conducting portion of the member against a rack tooth as at 3d and completes a circuit for audible warning devices 11, 11a, of which 11a may be a detonator. In order to terminate the signal, the current is switched off long enough for the member to run back off the rack so that when current is again switched on, the bi-metallic blade returns to the signal responsive position. The blade could be arranged to operate a signal in the straight condition if the supply is permanently cut off.

Inventors

No inventors recorded.

Bibliographic Details