This optically coupled circuit was found in the February 1968 Radio Electronics magazine. The circuit uses an LDR in modulation. Transistors are types of the time.
The original frequency of the Pierce Oscillator with bipolar transistor is given by the crystal, which...
Used in radio reception, this circuit was found in the February 1983 Radio Electronics magazine. The...
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....