G - Physics – 08 – B
Patent
G - Physics
08
B
340/159, 323/5
G08B 21/00 (2006.01) F25D 29/00 (2006.01)
Patent
CA 1084141
ABSTRACT OF THE DISCLOSURE An audible alarm device for use primarily with domestic freezers to provide an audible warning system as a malfunction of the freezer is disclosed. The device comprises a sensor cir- cuit including a Wheatstone bridge having a negative temperature coefficient thermistor in one branch, and a high gain differential amplifier to sense voltage differential across the bridge, and a transistor between the amplifier and an audible signal device. A primary power source normally powers the circuit with low volt- age direct current from a transformer having a rectified second- ary winding, and the device also has a secondary power source of low voltage direct current which comprises a battery providing reserve power for powering the circuit and activating the alarm device upon failure of the primary power source. In use, the thermistor which is positioned directly within the freezer compart- ment senses temperature increase in the compartment and triggers activation of the audible alarm and as an indicator of freezer malfunction.
240099
Mccord Robert N.
Mcfadden Fincham
Sharpe William R.
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