Here is an interesting circuit , it is used to make a kind of lock or locks for bicycles , it allows owners to implement a bicycle lock and electronic alarm with a low cost . The operation of the electronic lock is simple , it has a circuit that uses a tone generator IC UM3561 , this IC generates a sound when your bike has the protection wire that surrounds the wheel broken . Blocking Circuit with Alarm for Bicycle Circuit Diagram Click here to download complete project