Phone - Digital Telephones and Voice Over IP

Digital Telephones and Voice Over IP

The invention of the transistor in 1947 dramatically changed the technology used in telephone systems and in the long-distance transmission networks. With the development of electronic switching systems in the 1960s, telephony gradually evolved towards digital telephony which improved the capacity, quality, and cost of the network.

The development of digital data communications method, such as the protocols used for the Internet, it became possible to digitize voice and transmit it as real-time data across computer networks, giving rise to the field of Internet Protocol (IP) telephony, also known as voice over Internet Protocol (VoIP), a term that reflects the methodology memorably. VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone network infrastructure.

As of January 2005, up to 10% of telephone subscribers in Japan and South Korea have switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be "the next big thing." As of 2006 many VoIP companies offer service to consumers and businesses.

From a customer perspective, IP telephony uses a high-bandwidth Internet connection and specialized customer premises equipment to transmit telephone calls via the Internet, or any modern private data network. The customer equipment may be an analog telephone adapter (ATA) which interfaces a conventional analog telephone to the IP networking equipment, or it may be an IP Phone that has the networking and interface technology built into the desk-top set and provides the traditional, familiar parts of a telephone, the handset, the dial or keypad, and a ringer in a package that usually resembles a standard telephone set.

In addition, many computer software vendors and telephony operators provide softphone application software that emulates a telephone by use of an attached microphone and audio headset, or loud speaker.

Despite the new features and conveniences of IP telephones, some may have notable disadvantages compared to traditional telephones. Unless the IP telephone's components are backed up with an uninterruptible power supply or other emergency power source, the phone ceases to function during a power outage as can occur during an emergency or disaster when the phone is most needed. Traditional phones connected to the older PSTN network do not experience that problem since they are powered by the telephone company's battery supply, which will continue to function even if there is a prolonged power outage. Another problem in Internet-based services is the lack of a fixed physical location, impacting the provisioning of emergency services such as police, fire or ambulance, should someone call for them. Unless the registered user updates the IP phone's physical address location after moving to a new residence, emergency services can be, and have been, dispatched to the wrong location.