Electronic ignition system is designed for installation on vehicles contact ignition system. It has the following advantages: power sparks increased; the breaker contacts do not burn; don't need a resistor in the circuit of the coil ignition; with ignition on but not started the engine diagram smoothly without sparks is disabled.
Power sparks in this scheme depends on the temperature of the transistor VT2: high temperature of the engine decreases, the cold increases, facilitating the launch.
By opening and closing of the breaker contacts SK pulse passes through C1, briefly opening VT1 and VT2 At closing VT2 generates a spark. Capacitor C2 smoothes the pulse peak voltage. Resistors R6 and R5 limit the maximum voltage at the collector of VT2. When open the breaker contacts VT1 and VT2 are closed, in a long-closed contacts current through C1 gradually decreases, VT1 and VT2 closes smoothly, protecting the coil ignition from overheating.
The value R6 is selected for a particular ignition coil (in the diagram it is indicated for the coil B), for B value R6 = 11 kω.
For this coil is better to use as a transistor VT2 CTA.