Collection Schematic

This circuit will operate reliably from noisy or fluctuating power supplies and unlike many multivibrator circuits  is inherently self-starting when power is applied.
In this flasher circuit unijunction transistor G1 is used as a relaxation oscillator supplying a continuous train of pulses to the gates of the SCRs. Assume that SCR2 has been triggered into conduction and that lamp 2 is energized. The next trigger pulse from O1 triggers SCR1, this discharges C2 and the resultant commutation pulse turns off SCR2. The resistor R2 in the anode of SCR1 is of a value high enough to prevent SCR1 from latching on. SCR2 is re-triggered by the next triggering pulse from O1. Using the component values shown, the flash rate of this circuit is adjustable by R2  from 35 to 150 flashes a minute.