This two-digit circuit was found in the 1999 Radio Experimenter Handbook. It uses the CA3161 and CA3162 A/D converter pair common at the time.
In the figure we have the typical circuit of a Baxandall tone control applied to an operational...
August 2017 - Microchip's new ATtiny1617 8-bit AVR microcontrollers running at 20 MHz and 16 kB...
This Signetics circuit uses a double 555 (556) to generate tone bursts at frequencies determined by...