We found this circuit for video games in a Radio Electronics magazine from August 1977. The transistor can be any common RF type that reaches the desired signal frequency.
This filter is suggested by the Texas Instruments Linear Circuits Applications, 1986 edition. The...
This CMOS circuit was obtained in a 1980s documentation. The circuit has a 10-second time delay...
This circuit consists of a switched mixer with digital touch control. The circuit was found in old...