How do you configure speed-dial buttons on OBi handset? (No call key available)

[victorhooi]

I'm trying to setup the speed-dial buttons for an OBi 10XX handset.

I believe there are five soft buttons on the top right, that are known as "Line Buttons" in the configuration.

By default, all the buttons were set to "Call Appearance".

I changed it to "Speed Dial", and set the Service" to our VoIP service, and configured the name and number. We did this for Line Buttons 1 to 5 (i.e. all the buttons on page 1 of 2).

However, during a call, when we try to press the "Transfer" button we get the error message:

Code Select Expand

No call key available to make another call

The workaround we found from here is to add a Line Button slot set to Call Appearance, and set the MaxCalls to 8.

However, I have no idea why this works.

Also - is there an easier, or more logical way to configure speed dial buttons, and not have the "No call key available to make another call" error message?