Electronic multifunctional alarm circuit

This kind of alarm can use magnetic control, such as an electromagnet, to control the disconnection and connection of the dry yellow pipe, so that VT1 and VT2 are turned on, and drive the speaker
to make sound; it can also use light control, such as photoresistor RG, which can be controlled when subjected to When lighting, the conduction of VT1 and VT2 can also be controlled ,'. Make the speaker
sound; you can also use the square shoe with the open tube S to connect or disconnect, and also connect VT1 and VT2 to make the speaker sound.