This relay shield circuit for old computers was found in January 1983 Radio Electronics magazine. The relays are sensitive types with currents up to 200 mA.
This circuit has a voltage gain of 30 times and passband of 14 MHz. The circuit is from the 1974...
In the figure we have an oscillator circuit by Wien Bridge (Wien Bridge Oscillator). The frequency of...
This timer with 1 second accuracy was obtained in a 1973 documentation. The Buzzer is a low-power type...