This 1967 Philips circuit recognizes a light signal (visible or infrared) modulated by tone. The circuit makes use of components of the time that are equivalent to the current BCs.
Figure Bellow shows how to interface CMOS circuitos with TTL using the 4049 or 4050 IC. The power...
This circuit is from a manual from the 80's and the operational one used, uncommon nowadays, can...
Based on National Semiconductor's LM4130 reference circuit, this circuit was found in Internet...