This circuit was found in a 1924 Gernsback publication. The variable capacitors are dual. Listening is through a high-impedance phone.
This XR2208 application circuit was found in the April 1978 Radio Electronics magazine. The...
This circuit is from an old Elektor using components that are not currently common. The circuit is...
This 16-bit circuit was found in a 2005 Linear Technology application manual. The circuit uses...