I currently use a Panasonic DECT 6.0 KX-TGE270 cordless base with 5 remotes. I chose this because it was on sale at Costco at the time and had Bluetooth cell. Bluetooth cell allows me to link my cellphone to the phone base so that if the cellphone is nearby, it will also ring the cordless phones. The cellphone charges about 10 feet away from he base. I could add a second Bluetooth if I wanted.
When the cellphone rings I can see that it is a call on the cell by looking at the handset. I can also make a call from the handsets and choose whether it goes out through the OBI or through the cellphone.
The unit also has a built-in answering machine, which I don't use.
I have also successful used a Uniden DECT 6.0 base with a couple of remotes but I started having range problems.
You have to define "business" for me. :-) I have multiple "businesses" but little telephone business. I have probably 16 or more telephone numbers around the world, mostly because they were free. Most come in through
Voip.Ms and eventually end up at the Obi.
My call volume is quite small but I enjoy playing with the technology. I used to play quite a lot with telephones and lines. I once used a couple of .1 mf capacitors to join 2 phone lines and dialed "O" on both at the same time. It was funny to hear 2 Operators talk to each other.