Aastra 6757I User Manual page 115

Expansion Module Keys
5. Select from "Key 1" through "Key 36" (M670i)
or
Select from "Key 1" through "Key 60" (M675i)
6. In the "Type" field, select "Flash".
7. (M675i) In the "Label" field, enter a label to display on the phone for the key.
8. Click Save Settings.
Model 6757i IP Phone User Guide 109