From an old 1974 publication, this astable multivibrator causes a small incandescent lamp to flash at the frequency determined by C1 and C2. The capacitors can be 47 nF or another value nearby and the lamp can have more than 50 mA if TR3 is replaced by a BD135. The transistors of the original version can be exchanged for BC548. The power can be from 6 V to 12 V depending on the voltage of the lamp used.
