Conventional Bicycle bell has a number of disadvantages: inconvenient to work with, rattles while driving even on a flat road makes a sharp, unpleasant sound.
From these shortcomings are free electronic call. In addition, it is easy to change the volume and tone of sound. The device operates as follows. With the closure of the button S1 (Fig. 1) asymmetrical multivibrator transistors V1, V2 starts to generate oscillations of audio frequency. They come in single-stage amplifier V3, V4, assembled on a composite transistor. At the same time from the battery G1 charging the capacitor C2, which after the button is released continues to fuel the e-call. The tone of its sound increases and the amplitude decreases, resembling a siren. Resistor R3 limits current consumption and is made of cut spiral for electric.