These steps should work for all Aastra Wireless Handsets.
Keep in mind, there is a limitation of 4 handsets per base station.
During this process, keep the handset within 3 feet of the base station.
On the base station:
1. Press Options
2. Select Handset Pairing. (For a 57i CT, Select Preferences, then Handset Pairing)
3. Choose Pair and Press Select.
On the Handset:
1. Press the Menu key
2. Select Hset pairing
3. Press the Pair soft key
The base station and handset will attempt to connect, and then will display “Pairing successful” or “Pairing failed”.
If the pairing fails, remove the handset battery. Wait 5 minutes, replace the handset battery and try again. It may take a few tries to pair successfully. If the pairing continues to fail, you may have a bad unit. In this event, you should contact your distributor/reseller for troubleshooting purposes.