Dell Inspiron 1521 (Mid 2007) - Manual (Page 163)

Adding and Replacing Parts
163
Replacing a WWAN Card
NOTICE:
The connectors are keyed to ensure correct insertion. If you feel
resistance, check the connectors on the card and on the system board, and realign
the card.
NOTICE:
To avoid damage to the WWAN card, never place cables under the card.
1 Insert the
WWAN card connector into the system board connector labeled
"WWAN" at a 45-degree angle.
2 Press the other end of the WWAN card down into the securing tabs until
the card clicks into place.
1 metal securing tabs (2) 2 WWAN card
1
2