DrayTek have VoIP versions of most of their routers, and the functionality differs.

Basically, there are 3 groups:

  1. Residential models (Vigor 2100V, 2500V, 2700V, 2700VL) allow one telephone handset which can make and receive calls from VoIP and PSTN. Lifeline function ensures that the user can still dial emergency services (through PSTN) when the power is off (and the router and VoIP are not working).
  2. Business models (Vigor 2600V, 2800V, 2900V) assume that the business already has a PBX to handle the PSTN calls, and so have 2x FXS ports.  The business can choose to connect the FXS ports to trunk line ports on their PBX to allow all staff to make VoIP calls.
  3. Vigor 3300V is an Enterprise class multi-WAN router, and can accept 2 optional VoIP modules; where each module provides 4x FXS ports or 4x FXO ports.

Of course there is some blurring with new models and new firmware updates which incorporate more/better capabilities.  For example, the Vigor 2700VL incorporates both the LINE port feature of the residential models, and 2x FXS ports feature of the Business models.

Note that there are 3 types of telephone port :

  • FXS ports are for connecting to standard analog telephones.
  • LINE port (aka PSTN Pass-through) is for connecting to your telephone company’s PSTN line.
  • FXO port connects to telco PSTN line, and provides a gateway between PSTN and VoIP.

What is the difference between FXO and LINE ports ?
Both connect to the PSTN.  The difference is in how incoming calls are handled.

  • LINE port simply switches the PSTN LINE to your phone.  You answer your phone as you would normally.
  • FXO port is registered to your VoIP Provider. The FXO port answers the incoming PSTN call and provides a VoIP dial-tone.  The caller can dial any VoIP number.  Similarly any VoIP subscriber who knows the number of your FXO device can call it to get a PSTN dial-tone, and make PSTN calls.