Low Voltage Test (CB22158E)

This is a simple voltage tester for voltages from about 2V to about 15V with the indicated resistor and red LEDs.

Adjustable High Q Notch Filter (CB15815E)
We can implement this filter with more modern equivalent operational amplifiers, since the LM110 is...
Simple Stethoscope (CB18347E)
This stethoscope or amplifier for hearing aid using a crystal headset and microphone was found in a...
Divide-by-16 Counter - 4520 (CB176)
The normal use of a 4520 as a divide-by-16 counter is shown in Figure bellow. In the normal...