Scratch is the scratching noise that occurs mainly with old records. This high frequency noise is eliminated by the filter found in the February 1990 issue of Radio Electronics magazine.
In the figure we have the basic way of using the 3-and-a-half-digit counter 7107. The circuit is...
We found this 4-channel mixer in the August 1999 issue of Electronics Now magazine. The circuit can...
The circuit shown below was obtained from the National Semiconductor Linear Applications Handbook...