"Voiced" model tractor, car or locomotive immediately "comes to life", if you provide electronic simulator sound. Diagram of the device, mimicking the "voice" of the internal combustion engine, printed Yugoslav journal "Radioamator".
At the heart of the simulator is based on one of the many variants of LC oscillator two transistors of different conductivity type. The frequency of the oscillations regulate a variable resistor R1. If "motor" adds momentum, respectively increase the frequency of the generator, reducing the resistance R1.
Mode both transistors DC set selection resistors R1 and n. The voltage at the collectors of VT1 and VT2 should to be half of the supply voltage.
In EQ you can use any low-power silicon transistors KT3102, CT, KT315, CT, CT with any alphabetic indices.
When using the slide potentiometers type is easy to submit the form the frequency characteristic of the equalizer according to the position of the handles - in this case, his referred to as "graphic".
In your device, you can use any pair of low-power transistors CT, CT, KT315 (V1) and CT, CT, KT361, CT (V2) with any alphabetic indices. Output transformer and a driver from any transistor radio. Nutrition - battery 3336L.