The IP phone is designed to work within the VoIP (Voice over IP) environment. In essence, the IP phone allows you to make telephone calls over the IP network, converging voice and data over the same connection as an alternative to the standard PSTN. Calls made on an IP phone traverse the Internet, or the private IP network of a particular company.
To operate effectively, IP phones rely on protocols such as SIP (session initiation protocol), SCCP (Skinny Client Control Protocol) or any other of various proprietary protocols. The IP phone can be as simple as a software-based softphone, or as complex as a purpose-built hardware device that will appear to look like an ordinary telephone or a cordless phone. When an analog telephone adapter is in place, the ordinary PSTN phone can be used as an IP phone.
Some Common features of an IP Phone are: