This 1924 receiver uses a battery for the tube filaments and a high voltage battery for the amplifier and detector circuit. The speaker is kind of high impedance era.
This circuit was found in a Radio Electronics Constructor, English magazine from April 1976; The...
This circuit was taken from Maxim documentation from the 90s. The components are from the period....
This circuit was found in an Electronics World of 1968. It can be applied to any modern triac and...