We found this circuit for musical instruments in the March 1992 Radio Electronics magazine. The circuit has outputs according to the desired scale from a crystal oscillator at the indicated frequency.
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...