This circuit was found in documentation for radio amateurs of the 1980s. The circuit is intended to produce a tone for modulation in telegraphic transmissions.
Using a 555, this configuration appears elsewhere on this site. This is from American...
March 2017 - Mouser Electronics is sourcing the new Bluetooth Driver CC2564 from Texas...
Or integrated circuit used in this circuit two years 80 and little common in those days. The two...