A very simple electronic horn that require few external components and is very easy to construct can be build using this circuit diagram .  When the K switch is closed the oscillator formed by transistor T1 and T1 will generate a rectangular signal . This electronic horn circuit will consume a maximum output power around 40 watts  , so the audio signal of this horn circuit will be a little loud . This horn circuit require a 6 volts DC power supply . The T1 , T2 transistors must be a BC107 type or similar . The T3 transistor should be a 2N2613 npn transistor or BC 140,141, 2N1990, 2N2102, 2N2405 or other similar type . T4 transistor must be an AU106 PNP transistor or AU 113, AU 213, 2N5324 or other similar type .

The D1 diode that is used for protections of the T4 transistor must be an 1N5400 ,1N5401 ,1N5408 or other similar type .