Cycle burglar alarm

Claim 1

An alarm system for a cycle, comprising: a source of direct current; an electrically operable alarm device; a solid state gate controlled semiconductor triode rectifier having an anode, cathode and gating electrode; first circuit means connecting said current source with said alarm device and said rectifier in a first series circuit for activating said alarm device by current passing through said rectifier from the anode to the cathode, said rectifier having a high internal resistance so that it is normally in a nonconductive state until a voltage of predetermined magnitude and polarity is applied between said gating electrode and said cathode to reduce the electrical resistance to a low value, said low value of electrical resistance permitting current to pass continuously through the rectifier between the anode and cathode until the current in said first series circuit is interrupted; at least one normally closed switch means arranged to be opened by a person unauthorized to contact said cycle; first and second electrical resistance means; a voltage divider circuit connecting said current source with said normally closed switch means in series between said first and second electrical resistance means forming a second series circuit; and, a third circuit connecting said gating electrode with said second series circuit between said switch means and said second electricAl resistance means for applying a voltage of predetermined magitude and polarity to said gating electrode and normally maintaining said rectifier nonconductive between its anode and cathode, whereby when said normally closed switch means is opened said third circuit applies a voltage of predetermined magnitude and opposite polarity to said gating electrode to render said rectifier conductive between its anode and cathode.