Regal Startler Portable Electronic Burglar Alarm Vintage. Three alarms included. Model K6700. Simply hang on the inside of the doorknob.For all wood and non metallic doors. Takes one 9 volt battery, not included. Battery compartment is clean. Does not include original boxes. 6” height (closed). 10.5” height (open handle). Cannot confirm exactly how these work or if they work perfectly. From the 1970’s.