You can use the landline (LINE Port), SP1, and SP2 through the OBi, just not totally separately from the telephone connected to the OBi's PHONE Port.
If you're on a landline call through the LINE Port and need to make a toll call through SP1 or SP2 without hanging up on the landline call:
1. Press the FLASH button on your telephone. The landline call will be put on hold and you'll receive a new dialtone.
2. Place your toll call using SP1 or SP2.
3. When the call on SP1 or SP2 is over, press the FLASH button again to resume the landline call. If you press the FLASH button with both calls in progress, the landline call, the SPx call, and you will be conferenced together.