| 摘要 |
A control circuit for melody sound output of a door bell is provided to minimize component elements of circuit arrangement thereof and keep output sound for a predetermined time period by a single manipulation of a switch for outputting melody, buzzer sound, wind sound or voice sound according to the generation time of a charging current of a capacitor. A control circuit for melody sound output of a door bell includes a capacitor(21) connected between a positive terminal of a DC power supply and a base of a first transistor(11) electrically, and a switch(40) for connecting or shorting contact parts. One end of each of the contacts parts is positioned between the first transistor and the accumulator and the other end is connected to a negative terminal of the DC power supply. A diode(30) is connected between the switch and the first transistor. A second transistor(12) has a base electrically connected to a collector of the first transistor, an emitter connected to a melody element(50), and a collector connected to a positive terminal of the capacitor. As the switch is driven and a reverse bias is applied to the diode, a charging current generated by the accumulator is applied to the melody element for a predetermined time period through the first and second transistors.
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