Description: Ding dong doorbell switch s1 is push button switch on the door, without press the switch, the capacitance cannot be connected is not recharged, and capacitance voltage of 0 v, the reset has been in a low level condition, leading to the speaker doesn't work. When closed switch s1, the VCC current through the diode for capacitor charging, make its both ends of the voltage, and reset voltage also began to rise gradually. When the voltage of the capacitance increased to higher levels, namely the reset input port is the high level, the timer starts, composed of resistance, capacitance and diode oscillator start work, output frequency for f1. When disconnecting switch s1, resistance and capacitance circuit, capacitor began to discharge. At the same time composed of resistance, capacitance and diode oscillator start work, output frequency for ` 2 f. Restore low level is reset when the capacitor discharge end, timer stop working. In the speaker output termination, output current will make the speaker voice. Output frequency is not at the same time, the sound is different. This circuit has two kinds of different frequency, so the speaker will be issued a "ding" "dong" two kinds of different sounds. Specification: Package Name: NE555 doorbell kit Working voltage: 4.0-7.0V PCB Size: Approx. 4.3x 3.5cm/ 1.69x 1.38inch Kit horn: 8 Ohm 0.25W Color: As PicturesShown Package Includes: 1 Piece PCB board 1 Piece 8 Ohm 0.25W horn 2 Pieces 100MM red line 2 Pieces 100MM black line 1 Piece NE555 chip 1 Piece 8P IC block 1 Piece 100UF 25V Capacitance 1 Piece 10UF 25V Capacitance 1 Piece 6*6*5 keystroke 3 Pieces 103 ceramic capacitors 5 Pieces 47K resistance 2 Pieces 1N4148 Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement
