This circuit was obtained from an Electronics Now from the 90's. It generates the dial signal and the ring tone, serving for testing as well as for demonstrations.
MCP19124/5 Contains Independent Voltage and Current Control Loops Plus a Full Suite of...
A flash of light on one sensor or the touch of your fingers on the other type of sensor will turn...
This 1-transistor timer was published in Radio Electronics magazine in December 1960. The circuit has...