This was the situation, a year ago. 1 3CX Phone system. 2 Wired advanced VoIP phones. 3 Siemens Gigaset IP's. C470. When ringing one of the phones, with 2 phones, they all get the dial tone. Gigaset, or Wired, it worked. Then the 3CX and the Gigaset got a firmware update. This is the situation right now. When ringing one of the phones, with 2 phones, only one gets the dial tone. The other connects to the voicemail server. Strange is: the wired phones can be called with 2 phones, and the all get the dial tone. Even when trying a Snom M9, it doesn't work. Only one phone get the dial tone, the other connects to the voicemail. I don't get the picture. Another problem. We have a GoIP device.This http://www.discoverytelecom.eu/upload/iblock/e87/voip2gsm.pdf is the manual. Even following it to the letter, it won't register to the 3CX system. Please let me know if more details are needed. Thanks for all the input!