The selected circuit is from the Texas Instruments optoelectronics manual. With it you can receive optical signals in CW. Transistors support equivalents.
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...