This circuit is from a 1976 amateur radio manual. The transistor can be the BD136 and the frequency adjustment is done in a potentiometer. The supply can be done with voltages from 6 to 15 V.
Equivalent operational amplifiers can be used in this circuit of the 1990 Linear Databook,...
The SN76477 integrated circuit of the 1980s was a great success as a sound effects generator. Many...
This circuit for light data transmission (visible or IR) has a maximum speed of 1 Mbps and can be...