This circuit is from a Radio Electronics from March 1970. The integrated circuit used is one of the first for this purpose, being improved later leading to types that succeeded it.
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...