G.711 is the default pulse code modulation (PCM) standard for Internet Protocol (IP) private branch exchange (PBX) vendors, as well as for the public switched telephone network (PSTN). G.711 digitizes analog voice signals producing output at 64 kilobits per second (Kbps).
In G.711, the mu-law codec is used in North America and Japan, while the A-law codec is more common in the rest of the world. Both algorithms create a 64-Kbps digital output using an input sample rate of 8 kilohertz (kHz). G.711 employs a technology called packet loss concealment (PLC) that can minimize the practical effect of dropped packets. The effective signal bandwidth is reduced during silent periods by means of a process known as voice activation detection (VAD).
The G.711 algorithm is not new. It was originally introduced by Bell Systems in the 1970s and was formally standardized by the International Telecommunication Union (ITU) in 1988. Today, G.711 is commonly used in Voice over Internet Protocol (VoIP), also known as Internet telephony.