This 6-transistor circuit had excellent sensitivity using germanium transistors. The push-pull stage used two transformers, one drive and one output as we usually find at the time.
This circuit, to control air conditioning systems, was found in July 1984 Radio Electronics...
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
We found this circuit in an old American documentation (80's). The circuit generates sine signals...