The new technology has the ability to transmit a voice over Internet protocol process networks by using an Asterisk PBX. In present day, companies implement to produce different VoIP products of many features in market. This paper has an aim to introduce the VoIP and implementation of Wi-Fi based intercom system using ARM11 to based on Asterisk PBX. In this paper, we first introduce theory of VOIP. Next step is using ARM11 on Asterisk PBX .And Final step is the live project, live experimental set up and how to connect SIP voice traffic on Arm11.This paper shows the ability of voice calls to initiate using SIP with better stability and accuracy using Asterisk PBX.