This circuit supplies a load at SO1 when the load at SO2 is powered. The circuit is from a Popular Electronics from the 90s. Diodes and triacs must match the loads.
We can implement this filter with more modern equivalent operational amplifiers, since the LM110 is...
This stethoscope or amplifier for hearing aid using a crystal headset and microphone was found in a...
The normal use of a 4520 as a divide-by-16 counter is shown in Figure bellow. In the normal...