Telephone systems are an indispensable part of our lives – be it in the office or at home. We need these systems to keep in touch with others. Since the first telephone call made by Graham Bell, telephone technology has come a long way. Now, we even have satellite phones to communicate with another person located thousands of miles away and in a place with no modern communication systems available. Satellite communication can, in principle, cover every inch of the earth. The only thing that may disturb communication is extremely bad weather, but even that cannot stop the reach.
Mobile devices we can take on the go and even text information to someone on another device. Most analog systems have been replaced with digital telephony offering faster and better communication with less interference and noise. Whether you speak to someone next door, or a thousand miles away, the clarity and audibility will be the same.
Analog Telephone systems: This is a phone system that transmits analog signals and this is the reason why it is vulnerable to a lot of quality distortions. Analog signals are easily affected by magnetic and electric fields and distortions are very common. Voice quality depends on the quality of the signal and when the analog signals experience interference, the voice quality gets affected. Analog telephone systems are the cheapest in the market but they are not user friendly and they can’t be programmed. They are also slowly dying.
Digital Telephone systems: A digital phone converts an analog voice signal to a digital signal and transmits it over long distances. Digital signals are compressed, and once they reach the destination, are decompressed and converted back to analog signals. Since the digital signals move as compressed packets, the content is not affected by electro-magnetic interferences.
The signal quality of digital phones is higher and there is very little distortion. Since the chance of interference is mostly eliminated, the voice quality is not affected. These phone systems are very user friendly and can be programmed for specific tasks.
IP Telephone system: An IP Phone is used for making and receiving calls over an IP network instead of the PSTN. Control protocols such as Skinny Client Control Protocol (SCCCP), Session Initiation Protocol (SIP) and other protocols are used by the digital IP telephone systems. The telephone system uses the internet or an IPO network to make and receive the calls.
These telephone systems can be software based telephones called softphones or can even look like the traditional digital phones. In fact he digital phones that worked with PSTN can also be used by using analog telephone adapters (ATA). Power Over Internet and USB are used to connect the telephone systems to the network.
A few VoIP phones that use SIP are connected to the STUN client. The Session Traversal Utilities for NAT acts as firewall and even block the RTP/SIP packets. There are others that use the DHCP client which in turn can be used for changing the TCP/IP configuration. DHCP client facilitates automatic and centralized management of VoIP phones. The hardware used by the IP phones consists of the following:
- Speaker with microphone
- Display screen
- General purpose processor
- Power source
- Some even contain RJ-11 for connecting to the PSTN
There are also numerous mobile phones and PDAs that are Wi-Fi enabled and they contain SIP client software that can run IP telephony clients. The IP phones can be connected to the local area network (LAN) directly and, in case there are VoIP subscribers who want to work with their old phones, they can use sockets to do so.
Some of the most common features of VoIP phones are:
- Call Transfer
- Call hold
- Encrypted communications
- Dial with the name id
- Call park
- Conference calling
- A variety of other applications like weather report, live news etc.
IP phone systems or VoIP is the most sought after telephone systems as they provide reliable and seamless communication. These phones are very user friendly and come packed with loads of attractive features. These features can be used with the mobile phones and laptops also.