The purpose of this circuit found in an old Elektor is to light a lower power lamp when the bigger one burns out. The loads depend on the triacs.
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...