Last modified at 11/2/2013 11:53 AM by Koen Zomers
Telfort ADSL Internet in The Netherlands used to provide Zyxel P-2602HW-D3A modems with their internet subscriptions. They no longer provide these modems. These modems are equipped with two POTS ports and can sign in to two Voip providers. Telfort themselves provides a Voip service using the SIP protocol and has this modem connect to their Voip service to provide telephony services. I tried changing the configuration of this modem to connect to my 3CX PBX instead. For some weird reason, this is not possible. The Zyxel registers to 3CX PBX without any problems. In 3CX PBX Management it shows as being registered. However, as soon as you try to make an outbound call, the Zyxel will crash and automatically reboot.
 
To me it seems that Telfort deliberately has messed with the firmware on the modems to avoid "their" equipment being used with other cheaper telephony providers. This idea is only strenghtened by the fact that the Zyxel can register to two Voip providers, but does not have any way to set up dial plans. The only use of the two Voip accounts would then be to only be able to receive calls through two providers but always have to dial out through one provider. Can't imagine that to be the purpose of the feature.
 
I have also discussed this topic on the 3CX PBX forums: