Transfer calls SPA504G

Good morning,

In my company we are having some problems with the SPA504G phone. We can not transfer calls if we have one on hold. I give the example of the following situation:

  1. A call comes into the SPA (call A).
  2. The receptionist answers the call.
  3. While the receptionist is talking with the client (A), the screen displays the options ‘xfer’ and ‘conf’. Until then she can transfer the call.
  4. Then comes a second call, the call ‘B’, and then disappear options ‘xfer’ and ‘conf’ of the screen, and displays the options ‘Answer’ and ‘Ignore’. At that time the receptionist can not transfer the call ‘A’ until she answers the call B.

The hardware version of the terminal is the 1.1.0 and the software 7.5.7s.



SIP attended transfers require a free “line” on the phone for the enquiry. Whilst Asterisk won’t worry if a phone starts a third SIP session, the phone may want to pretend it only has two lines.

Also note that some SIP phones implement blind transfers as attended transfers which are automatically completed, so they need a spare “line” even for blind transfers.

Take a look at my pictures on my post on the Cisco forum for a workaround.
Basically, you will need a second line and the right XML setting to make it work.

It’s a Cisco bug that has not been fixed for years…

The actual bug: