This flasher of two incandescent lamps was discovered in a 1983 documentation and it has two frequency controls. The configuration is nothing new. It is an astable multivibrator in which the frequency is determined by both the base polarization resistors of the transistors and the coupling capacitors. Capacitors of 22 uF are used in the circuit, but to reduce the frequency of blinking, capacitors of 47uF or even larger can be used. By changing the value of the base resistances, the lighting time of each lamp can be modified significantly and, therefore, the operating frequency of the circuit. This change is made by two independent controls, connected at the base of each transistor. These are potentiometers, whose values can be between 4k7 and 22 k. The transistors used are of the BC548 type that withstand currents up to 100 mA, a current that must be the maximum of the lamps used. Equivalents such as BC237, BC238 or BC547, can be perfectly used. The supply between 3 and 9 V depends on the lamps.
