Voip technology means the technology transfers packetized voice over ip networks . network telephone is one of its typical applications . as the rapid progress of ip network technology , voip has become a hot topic in study and application Ip电话是指在以ip ( internetprotocol )为网络层协议的计算机网络中进行话音通信的系统，它采用的技术通称为voip ( voiceoverip ) 。
The gsm - r system supports functions of function number address , location decide address , vbs and vgcs . because of these functions , the gsm - r system can support the normal voice communication and specific communicaton for railway application 通过gsm - r系统的功能寻址、基于位置寻址、组呼叫、广播呼叫等功能,可以提供铁路运输指挥话音通信业务,也可提供站场、应急、施工养护和道口等专用通信。
In recent years , change has taken place in operation in the whole telecom network , data communication operation of ip has group up quickly , and it will gradually replaces voice communication to be the mainstream of telecom operation of the new generation 近几年来，整个电信网的业务流量正在发生本质性变化，以ip为代表的数据通信业务迅速崛起，并会逐渐取代话音通信而成为新一代电信网上业务的主流。
Hands - free speech communication is indispensable in audio and video conference systems , hot - line telephones and videophones , mobile radio terminals , digital isdn network etc . however , the control ( cancellation ) of the acoustic echo has always had a strong impact on the transmission quality in hands - free telecommunication ~ [ 1 - 3 ] conventional methods of acoustic echo control ( cancellation ) , such as echo suppression or gain control , may lead to the degradations in speech quality or make the speakers feel uncomfortable 免提式话音通信在移动电话、热线电话、车载电话及isdn网的电视电话会议等多种领域正得到日益广泛的应用。但至今的免提式话音通信中，仍免不了受回声引起的话音失真、甚至啸叫等干扰，大大降低了免提话音通信的质量。由于声回波对消问题尚未得到圆满解决，实现高质量的免提式话音通信仍是一个极赋挑战性的课题。
Carrier communication over high voltage power line has been developing for near one hundred years . it has many applications for voice communication in power distribution , data collection from tele - control instrumentation , and so on . however , using power line within one transformer area to provide internet access is a just recent development 高压电力线载波通信已有近百年的历史，它在电力调度话音通信、电力系统远动装置数据采集等方面取得了卓有成效的应用，但是利用一个台区的低压电力线建立internet接入网是近几年来国际上刚刚兴起的技术。
