This Wien bridge oscillator circuit uses a Texas Instruments 709 amplifier. It was found in an article in the September 1972 issue of Radio Electronics magazine. It is powered by a 24 V voltage.
We found this circuit in an old American publication. The transistors can be BC558 and diode 1N34....
This circuit will trigger an audible warning signal after the end of the pre-programmed timing. Using...
This is the commercial circuit for the TRF-44 amplifier sold in Japan in the 1960s. The circuit...