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.
The S-meter is a signal strength meter used in communication receivers. This circuit was found in...
National Semiconductor suggests the circuit in the figure that uses two operational amplifiers of type...
This circuit was obtained from Linear Technology documentation from the 90s. The circuit uses...