IP Telephony vs PSTN

IP telephony (Internet Protocol telephony) uses the internet to deliver calls as packets of data on shared lines. Also know as VOIP it is the real-time transmission of voice signals over the internet or private data network.

IP telephony was built upon two foundation blocks, the telephone and the internet. It took over 40 years for both the telecommunications industry and the computing industry to develop the VOIP service. This technology has been brought to the forefront of communications by the freedom and flexibility of the internet. The use of IP services is continuously growing within the call centre industry . This is mainly down to the flexibility and the low costs that are involved to make outbound calls.

PSTN (The Public Switched Telephone Network) is the network of the world’s public circuit-switched telephone networks. The PSTN is made up of fiber optic cables, microwave transmission links, communications satellites, undersea telephone cables, telephone lines and cellular networks. All of this equipment is inter-connected by switching centres which subsequently allows any telephone in the world to communicate with another.

Bell Telephone Company were the first organisation to provide PSTN in the United States.

PSTN was once a network of fixed-line analog telephone systems. It is now almost entirely digital and includes both mobiles and well as fixed telephones.

Over the years the PSTN network architecture has had to evolve. This was to support the increasing volumes of calls and subscribers, worldwide connections, direct dialling and more.

PSTN have dedicated lines. The system itself works by setting up a dedicated circuit between two points for the whole duration of the call. These systems are based on copper wires which carry analog voice data over the dedicated circuits.

This is in vast contrast to the newer IP telephony network. All channels for the IP telephony network are carried over one internet connection. This network is based on digital technologies and the information travels to its destination in individual network packets. Unlike PSTN long distance phone calls can be made at very little or no cost at all to the customer. IP telephony phone calls themselves can be marketed as being ‘free’. This is not the case with PSTN where calls are usually charged on a per minute basis or bundled minute subscription.

Call management features such as, call waiting, caller ID, call holding etc, are usually available at no additional cost to IP telephony subscribers. You would most likely incur a charge if your were to require these kind of features on PSTN.

PSTN and IP telephony differ heavily in terms of the equipment that they require and also how they go about delivering their calls. Whilst PSTN require physical lines IP telephony is all digital and requires nothing more than the internet to be fully operational.

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