Alarm for a blind

Claim 1

A self-contained portable alarm device, suitable for fitting to a blind of the type of venetian blinds, vertical louvre blinds and roller blinds and for insertion into a fold in a curtain, which alarm device comprises: (a) a printed circuit board for fitting to said blind and for insertion into said fold; (b) a piezoelectric motion sensor mounted upon said printed circuit board; (c) said piezoelectric motion sensor including a flat plate of piezoelectric material mounted to flex in response to motion in its vicinity and thereby produce electrical signals therein; (d) an amplifier circuit in said printed circuit, electrically connected to said piezoelectric motion sensor to receive electric signals produced in said sensor and to amplify said signals; (e) a solid-state switch mounted upon said printed circuit board and electrically connected to receive amplified signals from said amplifier circuit; (f) an audible alarm mounted upon said printed circuit board and electrically connected to said solid-state switch to be activated by said switch; (g) a battery mounted upon said printed circuit board and connected to supply electric power to said amplifier circuit and to said audible alarm; (h) an on-off switch electrically connected to interrupt said electric power supply from said battery; and (i) time delay means upon said printed circuit board to delay said alarm being made operative for a predetermined short time after said on-off switch has been switched on.