We found this simple protection with zener diode in a 1967 Motorola documentation. The zener diode is 18 V, but the components can be changed for operation with other voltages.
This instrumentation circuit is from the June 1986 issue of Radio Electronics magazine. Equivalent...
This 2000 circuit can be used to match the low impedance of a microphone to the high input...
This sensitive two-transistor circuit was found in the June 1965 Radio Electronics magazine. The...