Hello, I'm using Elastix 1.6-12 mainly with softphones (X-Lite). We use attended transfer functionality (*2) and it works great. But we have 2 hardware phones - produced by Siemens and attended transfer is not working at all using them. I also tried it on the Grandstream BudgeTone GXP-200 which I had borrowed and it also didn't work. It seems that no DTMF tones are recognized using the hardware phones. What can I check to solve that problem?