An IP phone is a device which uses an internet connection to make and receive phone calls. Essentially, there are two types of IP phones: Hardware based IP phones that use an adaptor to plug your standard home telephone into your home network and software based IP phones (or soft phones) that consist of software which allows telephone calls to be made directly from your computer.
Hardware-based IP Phones
Hardware based phones consist of an ATA (Analogue Telephone Adaptor) which connects your PSTN to your home network. Popular ATA products in the market include CISCO’s ATA 180 Series and the Sipura SPA-3000. Calls are made directly using the telephone plugged into the network.
PSTN (Public Switched Telephone Network) refers to the collection of interconnected telephone networks that exist in today’s world. It is also popularly referred to as POTS (Plain Old Telephone Service). When you make a call, your local carrier routes it through a series of physical switches which culminate in your phone being connected to the other person’s.
Software-based IP phones
Software based phones simply refer to pieces of software that run on your computer and allow you to make telephone calls through them. Popular products include software such as Skype, Google Talk and the Yahoo Messenger. The latter two allow you to make phone calls only to people using the same service while Skype transcends these boundaries and allows you to call regular phone users (at a cost of course). Soft phones need to be used with peripheral speakers and microphones.
Advantages
IP phone services are very cheap compared to traditional phone services. Their biggest savings come from the lack of taxes and fees. One of the key advantages of IP phones is their ability to maintain local long distance. IP phones work with virtual telephone numbers. By using a virtual phone number with an area code similar to the place you are calling to, local calls can be made from even half way across the world. Similarly, anyone contacting you from that area will also be making a local call thus avoiding any tolls or cess in the process.
IP phones also help integrate various tasks such as managing caller id’s, call waiting and forwarding etc from the comfort of a personal computer.
Disadvantages
On the flip side, however, IP phone services are not always reliable. Voice quality generally depends on the quality of your internet connection and 911 phone calls cannot always be made using these phones. The ATA (Analogue Telephone Adaptor) also runs on electric power and stops working in case of a power failure or malfunctioning internet connection. High end ATA’s however automatically switch to the POTS line when this happens.
The PSTN
The term PSTN (Public Switched Telephone Network) refers to the collection of interconnected telephone networks that exist in today’s world. It is also popularly referred to as POTS (Plain Old Telephone Service). When you make a call, your local carrier routes it through a series of physical switches which culminate in your phone being connected to the other person’s. This entire process is referred to as circuit switching.
The PSTN is also the corner stone of the internet’s infrastructure. Since ISP’s (Internet Service Providers) pay long distance providers for access to their infrastructure and share circuits through packet switching, Internet users avoid having to pay usage fees to anyone other than their ISP’s.
