G-Protection is actually a combination of features--including a memory buffer and variable-speed platter (as found in many other CD and minidisc players) plus a specially refined, quick-reactive laser beam (unique to Sony) that rides out the jolts like nobody's business. Some other CD players with memory buffers cut the high frequency edge off the music, but not so in the G-Protection version. When this circuit is engaged, Sony's excellent CD sound quality remains intact.

In the process of rethinking player mechanics, Sony has also downsized components and improved energy efficiency. That's why the D-EJ715 manages to be so slim (just 1 inch tall, 5.25 inches wide, and 5.625 inches deep) and lightweight (6.4 ounces, excluding accessories). That's also why it runs for so long.

With the supplied rechargeable nickel-cadmium batteries installed, you can enjoy up to 8 hours of playing time--that's with G-Protection engaged and the CD player placed on a flat and stable surface. (Not incidentally, these batteries recharge in the player in just three hours with the supplied AC adapter attached, a cute trick.)

With a pair of AA batteries in place, the playing time shoots up to a maximum of 32 hours. (Early CD portables sucked all the juice out of four alkalines in just four hours.) The LCD screen on the lid of the D-EJ715 includes an icon that shows the remaining battery power.

We also like that there's just one slot for installing either rechargeable or throwaway batteries on this model. On some other CD portables, including