Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The circuit has a flat response from 10 Hz to 700 kHz.
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...