When buying a digital recorder it is important to realize that the technology is changing very rapidly in this area. This results in two things to watch out for - getting a unit that is obsolete, and getting an orphan technology that is no longer supported.

When you are considering buying an item it is a Very Good Idea to google the make and model of the item, find the manufacturer's web site, and download the complete owner's manual. These documents are sometimes dauntingly large, they can run to hundreds of pages. It is very important to go through these documents thoroughly and find out :  what is the means of data transmission, what is the media format or formats supported (hard disk, flash, memory card Zip drive, SCSI, etc), what is the sampling rate of the device, and whether it needs other devices, such as a digital mixer, for it to work.

The small advertising blurbs usually included in the Ebay announcements are often quite bloated in their praise for the item's capabilities while being vague about its actual operation. Sometimes the descriptions, especially the title, are just wrong - they may declare that a recorder(or mixer) is digital when it is actually analog. Similarly, when you enter a search for a "digital recorder"  you will undoubtedly end up with a list that includes many analog or other undesired items. My search for "digital mixers" (necessitated by the purchase of a digital recorder that did not include an mixing interface) resulted in a list that included handheld food mixers!