This circuit was found in a Radio Electronics from 1970. The coupler with LDR is from that time, but the circuit can be adapted to use modern components and act as a shield.
This amplifier has a gain of 45 dB (100 times) operating with audio signals from 50 Hz to 25 kHz....
This circuit can be controlled by an LDR causing an LED to flash at a frequency given by C2. The...
The basic idea of the circuit shown in the figure is to increase the brightness of an ordinary...