This circuit reproduces the dial noise in a small speaker. The transistor can be a general-purpose type. We found it in an 80's Electronic Design.
In the same way that we can regulate the voltage in the positive branch of the circuit, we can...
Based on the MC1488 or MC1489 operational amplifiers, this circuit has a 5000V isolation driving a...
Found in the July 1968 Supertena Bulletin of a Popular Electronics, this receiver makes use of the...