This circuit was found in a 1962 publication. At the time there were high voltage batteries like the one used in this project. For a current version you can use a transformer inverter, as the consumption is extremely low, in the order of less than 1 mA for this sector. The transistors can be BC558 to TR1 and BC558 to TR2; The handset must be magnetic from 200 ohms to 2k ohms. The critical component is Geiger tube.
