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 circuit is powered by 1.5 V and has a long lifespan as it consumes only 320 uA. The circuit is...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
With this circuit, from a 1991 publication, it is possible to regulate the output of a symmetric source...