Internet Telephone Devices

IP-telephone is not really a new concept and is now available on the market for many years, it's no more in testing mode. People don't know exactly what a voice over ip device is. What is it, how does it work?

Here you will find some information about voice over IP devices.

A voice over ip device can be classified in three general categories:


end stations (such as phones),
gateways and routers,
and controllers.

Like everything else in IT, every category has a specific function that it performs. And if you combine all the functions you will get a complete voice over ip system.

Hardware and software VoIP phones

There are two types of VoIP phones: hardware and software.


A hardware phone is a physical device, very similar to your common phone; it has a handset, dialpad, etc. The only thing that is different from your ordinary phone is that it connects to an Ethernet network rather than a telephone network. IP phones are built with all the necessary hardware (and software) to digitize your voice (i.e., codecs) as well as setup and make calls (i.e., signaling and transport).
Software-only phones, or "soft" phones, use the PC's capabilities to communicate with other PC's over the Internet, by using the PC's sound card, CPU and network card as part of the phone's hardware, and thus, enable a PC to become an IP phone.

Gateways

A IP-telephony Device is a voice over ip device that connects the VoIP network to your public telephone network (PSTN). In this way, you can make calls and receive them, from your PTSN, even if you are using an IP-based system, just like your traditional phone. Depending on the type of the gateway, they are equipped with analog/digital interfaces in order to connect to your local telephone company. With so many options available today, gateways are also capable of transcoding (changing the signal from one codec version to another so that the voice over ip device can communicate with the rest of the network). For example, a gateway uses G.729 codec, while your PTSN network uses a G.711 codec.

Controllers

VoIP controllers, also called IP PBXs, manage the VoIP network. They are actually tools that you can use to configure your IP phone: restrict access, enabling functions and passwords, allowing/not allowing certain options, etc. Plus they are performing all the functions of a traditional PBX. IP PBX controllers are PC-based, running a standard OS (such as Microsoft Windows, Linux or Sun Solaris, but very different) with additional software to control the voice over ip systems. These voice over ip systems can provide APIs to extend vendor-provided or user-written features and functionality.

Routers

Voip Routers are voice over ip devices that decide where the IP datagrams should go, between networks, from the source to the destination. Routers are inter-network equipments that help a LAN connect to a WAN; therefore the router's capability to ensure correctly handled high-priority traffic is very important. Since WAN speeds have generally less bandwidth than a LAN, proper packet queuing and prioritization is in order to ensure good voice quality across the path.

Internet Telephone Devices
By Jim Francisto

Enjoy to talk with VoIP !