CD-ROM 'digital' port

On many CD-ROM drives, there is a 2-pin 'digital' port with pins labeled 'D' and 'G'. Is there a standard specification for this or does it vary across model and manufacturer?

Thanks.

'D'

across

D = data G= ground

It's the same on all CD-ROM drives and it's called a SPDIF interface. It transmits a digital audio signal. You can use it to decode the audio signal by an external D/A converter. Al you need is and IEC958 decoder with a SPDIF interface and a D/A converter.

Apparently there's the occasional unit that uses the standard voltages (0-1V, I think), while most will use 0-5V... so be ready for that.