The LED with integrated flasher is connected in series with the base-emitter junction of transistor Tl. Thus, the l
oad connected to K2 is switched on and off in rhythm with the flash rate. This load can be a relay or a lamp. The maximum collector current of the transistor (of the BD139 = 750 mA) must not be exceeded. If that is not sufficient, a power Darlington can be used, which will give some amperes. The current drawn by the circuit under no-load conditions amounts to 20 mA.