Hi Cruch,
It is an IDE connector. But lately, we have been calling it the "Expansion connector". If you have older firmware on the QM2000, you can connect a CD-ROM or DVD drive and put a CD into the drive. If your CD has special files in special places, it can play. This is the technology tha the CD2000 is based on.
More recently, we have changed the firmware and this connector is used to interface to our QM2000.NET adapter board, which currently allows direct network communication with the QM2000, and in the future, may provide USB connectivity as well.
Best regards,
William Benner