This circuit was found in a 1965 Electronic Design. What it does is respond only to positive pulses (above zero volts) and can be used in automation systems.
July 2017 - Mouser Electronics has in its stock the new infrared (IR) emitters from OSRAM Opto...
This circuit is from a 1966 NASA documentation. The circuit uses a photodiode as a sensor. The other...
This doorbell or buzzer as announced in a 1990s US publication uses an operational amplifier that admits...