This circuit was found in a Dutch documentation from 1970. The circuit makes use of semiconductors that have current equivalents and is indicated by a 0-5 mA milliammeter.
Found in a Popular Electronics from the 90's, this circuit uses integrated from that time, today...
This tone generator for CW was found in a publication by Gernsback from 1960. The circuit makes use...
Based on the LF256 operational amplifier, this circuit was found in the September 1989 issue of...