We found this circuit in Radio Electronics from the 1980s. The circuit uses an optical coupler with LDR. The operational can be the 741 since the original is a double version of it, and the power supply must be symmetrical.

We found this circuit in Radio Electronics from the 1980s. The circuit uses an optical coupler with LDR. The operational can be the 741 since the original is a double version of it, and the power supply must be symmetrical.