The transistors of this circuit found in an English 1980s documentation may be the modern BC548 equivalents. The circuit is battery powered and the earphone must be crystal.
January 2017 - Texas Instruments' new 16-Bit SAR (Analog to Digital Converter) DC is available from...
I found this circuit in a 2005 Wireless World and it is ideal for driving high power white LEDs....
This article is from a publication by A. Fanzeres from the 70s. We kept the original text. Using a...