Voice over Internet Protocol, or VoIP, telephone products connect to VoIP, or Internet telephony, systems, which use packet-switched telephony to transmit calls over the Internet as opposed to the circuit-switched telephony used by the traditional Public Switched Telephone Network (PSTN).
How it Works
VoIP telephones look and largely function like standard phones, but they have built-in IP technology and an RJ-45 Ethernet connector instead of the standard RJ-11 phone connector that enables the VoIP phone to connect directly to a router for making and receiving IP calls. A standard phone can also function as a VoIP telephone when used with an analog-to-digital converter called an ATA, or analog telephone adaptor. Another option is to bypass the phone entirely and simply use a VoIP-capable computer to make and receive IP calls.
Recommended Reading: The Difference Between VoIP and PSTN Systems.