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.
This transmitter operates in the FM band emitting beeps that can be picked up on a common radio at...
This configuration can be found in other articles on this site. This was obtained in 1998...
This circuit is from a documentation from the 70s. Thus, the original transistor no longer exists,...