In the English magazine "Practical Wales" printed a relatively simple circuit sirens for models and toys. Generator sound is made of two semiconductor devices VT1, VT2 included under the scheme unijunction transistor. Sound vibrations are amplified double emitter follower transistors VT3, VT4. As the speaker used a regular phone earpiece with resistance 32-64 Ohms. By manipulating the switch SA1, change the mode of the generator: when charge and discharge of the capacitor C2, the tone of the whistle increases, reduced.
Fig. 1
As VT1 can try to use a transistor CT or KT361, other transistors can be KT3102, KT315. All semiconductor devices - any alphabetic indices.
Literature
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