Optical CD-ROM Output

Many CD-ROM drives have in addition to the analogue output also a digital S/PDIF output, in the form of two pins, typically next to the analogue connections and which are generally unused. It is quite straightforward to connect a Toslink module to these pins to add an optical output. The 5-V power supply that this module requires can easily be tapped off the power supply connector of the drive. But it can also be done simpler and cheaper: just connect a series resistor and an LED (Figure 1).