Optical sensor for PC (CB20548E)

This circuit was found in a PC documentation from 1996. It can be used as a shield with modern microcontrollers.

Microchip Launches New Development Board for Designing with 16-bit and 32-bit PIC® Microcontrollers
The New Microchip development board is targeted to designers who work with 16- and 32-bit PICs....
Thought Recorder ISD1000A (CB25688E)
The circuit shown was found in the February 1994 issue of Electronics Now magazine. The circuit...
555 Timer 555 (2) (CB3983E)
The circuit presented is suggested by Mullard (Philips) in an old manual. The circuit uses a...