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.
We found this circuit in a Motorola documentation from 1968. Phototransistors are common and...
This circuit was obtained from a 1978 Practical Wireless. It makes a speaker emit sound when there...
This circuit was found in Sprague Electric documentation from the 90s. The circuit uses a...