Samsung Releases M6 HM320JI 320GB Laptop HDD

Samsung has released the Spinpoint M6 HM320JI 320GB 2.5-inch notebook hard drive, featuring a 5,400rpm rotational speed, Serial ATA interface, and 8GB of cache memory.

The M6 HM320JI 320GB utilizes perpendicular magnetic recording (PMR) technology and has an optional Free-Fall Sensor that protects data from drops, as well as an optional Rotary Vibration Controller that minimizes the influence of external vibration.

The Samsung Spinpoint M6 HM320JI 320GB HDD is priced at $249 and is available now.

Hard drives with a capacity of 320GB, which is the largest in the industry for 2.5-inch form factor, have been already announced by Fujitsu, Western Digital, and Toshiba.

Source

The free fall sensor is NOT “optional”.
I think you misread the original publication which says it is “optical”.
Very important difference!