asterisk users - Jul 2003 - Call transfer between two phones on the same ATA

Hi,

It is possible to transfer a call between 2 phones connected to the same
ATA186?
When I try this, the transfer is done to the voicemail of that user.
I can transfer the call to another external phone, but not to the one on the
same ATA.
This is a normal behaviour?

Thanks,
Dan