3887909 is referenced by 13 patents and cites 10 patents.

An alarm device having an extendible cord control element the outer end of which is attached to an object, such as a window or door, to place the cord in predetermined tension with the cord acting directly on a switch arm to effect an alarm signal upon a change in tension of the cord resulting from breaking or pulling thereof.

Title
Alarm device
Application Number
05/248,050
Publication Number
3887909
Application Date
April 27, 1972
Publication Date
June 3, 1975
Inventor
Jorgensen Leland DeVon
Beiswenger John L
Agent
Johnson Dienner Emrich & Wagner
Assignee
National Presto
IPC
G08b 13/08
G08b 13/00
G08B 17/06
G08B 13/02
G08B 13/08
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