Ioannis,

Yes, you are right about T1 and T2 keeping the voltage low on the LM2595 chip. However, I am still not convinced with this circuit. After looking at the datasheet for T2, it seems to me like the Drain and the Source inputs should be swapped for a proper grounding on LM2595. The current should be flowing away from the ground in LM2595, not towards it.

Also, the maximum VGS voltage on T2 is 20V, so if for some reason T1 fails T2 would also be fried. I don't know why Elektor designed this circuit without a transformer, and I agree with you that this is very dangerous.

Robert