Using VoIP on your current telephone system
If you would like to keep you existing telephone system and use VoIP, you will need to an Analogue Telephone Adaptor (ATA).
The ATA converts VoIP services back to Digital (ISDN) or Analogue (PSTN) lines.
The ATA then is connected to your telephone system.
ATA's come in 2, 4, or 8 lines.