VOIP telephone

INTRODUCTION

VoIP Voice over Internet Protocol is a revolutionary technology that allows you to make calls using your broadband connection instead of your regular phone line. It is generally used to make international calls.
Traditional TDM switch is being in use for so many decades serving telephony services. It has some limitations in supporting so may service which are available though IP networks. TDM switches are big in size, complex hardware with associated programming interfaces. With the advent of modern technology, so many services are moved on to IP networks. Our traditional TDM switch also moved to IP and named IP PBX. 

TECHNOLOGY

Traditional phone networks use circuit switching to connect calls. When you speak, the circuit is continuously open, whether you are talking or not, wasting a lot of network space and time. When you disconnect, the circuit closes. Nowadays, the system has been digitized so that fiber optic cables are used (for most of the connection, not all the way), which carry several calls at the same time. Calls are transmitted at a fixed rate per second.

IP PBX is the software implementation of the TDM switch. IP PBX offers all the services to users as available from TDM switches. Even some specialized services like multiple presences and global portability are available which are not in traditional TDM switches.
 
Voce is digitized and packetized for transportation across the IP network. At the receiving end these packets are converted to analog signals. This is known as VoIP- Voice over Internet Protocol. There are so many IP PBX is the software implementation of TDM switch. IP PBX offers all the services to users as available from TDM switches. Even some specialized services like multiple presences, and global portability are available which are not in traditional TDM switches. Voce is digitized and packetized for transportation across the IP network. At the receiving end these packets are converted to analog signals. This is known as VoIP- Voice over Internet Protocol. There are so many IP PBXes available commercially across the globe. Some open-source IP PBXes are here for our experiment. Asterisk IP Communication server is open-source application software. It runs on the Linux operating system.

IP PBXes are available commercially across the globe. Some open-source IP PBXes are here for our experiment.
 
Asterisk IP Communication server is open-source application software. It runs on the Linux operating system.

VoIP uses packet-switching technology to connect calls. Unlike circuit switching, this network does not waste any space. If you are talking it means that the other person is listening. This is not a full connection. It can be likened to using only half the connection at a given time. Also, dead air time, when nobody is speaking, is not used in the connection. Removing all this from the connection brings down the space used. So signals are sent only when it is needed, that is, when the connection is being used at a given point of time. Hence there is no wastage. Since the data is chopped up into packets, it is called packet switching.

The voice is converted to data on sending which goes like an email. The packets contain information on where they are to go. Several routers along the way receive and send the packets along until the final one reassembles the packets according to the instructions in it and converts it back to voice.

Benefits

Cheap International rates: VoIP calls are known to be much cheaper than equivalent services offered by traditional phone companies. A single broadband network is used to carry both voice and data. This substantial cost saving occurs because the technology allows the network to carry several calls in the same amount of space that normally carries a single call in a traditional phone network. Also, the data is compressed allowing more space and thus, lower rates.
Convenience: It is easy to operate using one of two options: Using a computer to make calls or using a special broadband phone to make calls rather than a PC.

Receive Calls anywhere: You can also receive incoming calls on your VoIP phone if you take it along on a trip. All you have to do is to plug it into the network.
Call center on the move: Call center agents can work easily from anywhere as long as they have a good Internet connection. There are also advanced call service options available from some carriers. These features use caller ID information to allow you to make a choice about how calls from a particular number are handled. The above-mentioned services can either be free as a part of your billing plan or it can even be chargeable as you subscribe to them so it is always better to check with the provider before you subscribe.

Limitations

* You may not be able to emergency and dial toll-free services such as 1800 numbers or other free services.
* The Internet connection must be of a reasonable quality and speed for a clear and smooth connection. 
* VoIP being dependent on the broadband line is susceptible to all the limitations of the Internet.
* It is also susceptible to computer issues such as processor specifications. Also, the quality of a call may be affected if you are using the computer for an intensive application while on a VoIP call.

DIALLING OPTIONS: 

ATA Analog Telephone Adaptor:
The ATA allows you to use a standard phone to make VoIP calls. The ATA is an analog-to-digital converter. It takes the analog signal from your traditional phone and converts it into digital data for transmission over the Internet.
 
IP Phones:
These specialized phones look just like normal phones with a handset, cradle and buttons. But instead of having the standard RJ11 phone connectors, IP phones have an RJ45 Ethernet connector. IP phones connect directly to your router/modem and have all the hardware and software necessary right onboard to handle the VoIP call.

DIALLING OPTIONS: 

 

IP Phones

These specialized phones look just like normal phones with a handset, cradle and buttons. But instead of having the standard RJ11 phone connectors, IP phones have an RJ45 Ethernet connector. IP phones connect directly to your router/modem and have all the hardware and software necessary right onboard to handle the VoIP call. Wi-Fi phones allow subscribing callers to make VoIP calls from any Wi-Fi hotspot.

Soft Phones

A small software applet known as softphone installed on to a PC can be used to make and receive calls. With a headset, one can communicate.

Voice over IP (VoIP) can be described as the ability to make telephone calls and send faxes over IP-based data networks with a suitable Quality of Service (QoS). The voice information is sent in digital form using discrete packets rather than via dedicated connections as in the circuit-switched Public Switched Telephone Network (PSTN). 

Currently, there are two major international groups defining standards for VoIP:

International Telecommunications Union, Telecommunications Standardization Sector (ITU T), and Internet Engineering Task Force (IETF).

The H.323 recommendation was developed in the mid-1990s and is a mature protocol.

SIP (Session Initiation Protocol) is an emerging protocol for setting up telephony, conferencing, multimedia, and other types of communication sessions on the Internet.

SIP Overview

Session Initiation Protocol (SIP) is an ASCII-based, peer-to-peer protocol designed to provide telephony services over the Internet. The SIP standard was developed by the Internet Engineering Task Force (IETF) and is one of the most commonly used protocols for VoIP implementations.

 

Advantages of Using SIP

Some of the advantages of using SIP include:

1. The SIP protocol stack is smaller and simpler than other commonly used VoIP protocols, such as H.323.