We found this circuit in an old QST magazine. The circuit is powered according to the thermostatic relay used.
It can be obtained from Mouser Electronics new superFETs III from Fairchild for voltages of 700 V...
This circuit was found in a 1969s American documentation. With modern components, it can be used...
The figure shows how to change the frequency of a 5 V LED blinking. The capacitor can have other...