The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
This 12 or 13.8 V stabilized source is suitable for experimental FM transmitters that require...
This circuit uses a TL071 to differential amplify the signals from a microphone and thus reduce...
Found in Motorola documentation from the 90's, this circuit charges the capacitor with a constant...