Sony MSW-900P Operation Manual page 230

2
Hold the memory stick with the notch facing downward and the
arrow facing toward you, and insert the memory stick into the
memory stick insertion slot until it clicks into place. Then, close the
cover.
4
Note
If it does not fit into the slot properly or if there is some resistance when
you insert it, the memory stick may be turned around or upside down. Do
not force the memory stick into the slot. Confirm the direction of the
notch and arrow on the memory stick before inserting the memory stick,
and then try inserting it again.
4-118
Chapter 4 Adjustments and Settings for Recording
Memory stick
Inserting the memory stick.