Found in an Electronics Now from the 90s this mixer has several inputs. The integrated circuit can still be found easy and the power supply need not be symmetrical.
This circuit, from an 80's publication, detects the SCA (Announcer Eliminator) signal from FM...
The circuit is from the Linear Application Handbook. The resistors determine the voltage applied to...
USB58xx and USB59xx Devices Integrate a 2:1 Multiplexer to Support Reversible Connection of USB...