line phones with bluetooth.

I have a Gigaset deskphone with bluetooth, I don't know if you can pair it with a bluetooth headset, but I have paired it with a smartphone.

When the smartphone rings you can answer the call on the deskphone or any of the DECT handsets, unfortunately every time I've used that feature people complain at the call quality, though call quality over bluetooth to the car handfree is fine.

I guess I'm saying try before you buy ...

What are you trying to achieve? (i.e. use a bluetooth headset on a line phone, or integrate a mobile into the mix?)

I am purchasing a hearing aid that will connect by Bluetooth to a telephone.

I have a Seimens Gigaset dect handset. I use it with a Bluetooth headset all the time.

Bluetooth doesn't have brilliant range so you need to carry the handset with you, in a pocket, as you walk around the house.

Also the Bluetooth headset takes over both the microphone and speakers, I'm not sure how this works with a hearing aid.

What's supposed to happen is that if the HA doesn't report a microphone then the existing microphone will still work. Whether that works in practice is less predictable.