Telephones were originally connected directly together in pairs. Each user had separate telephones wired to the various places he might wish to reach. This became inconvenient when people wanted to talk to many other telephones, so the telephone exchange was invented. Each telephone could then be connected to other local ones, thus inventing the local loop and the telephone call. Soon, nearby exchanges were connected by trunk lines, and eventually distant ones were as well.

In modern times, most telephones are plugged into telephone jacks. The jacks are connected by inside wiring to a drop wire which connects the building to a cable. Cables usually bring a large number of drop wires from all over a district access network to one wire center or telephone exchange. When the user of a telephone wants to make a telephone call, equipment at the exchange examines the dialed telephone number and connects that telephone line to another in the same wire center, or to a trunk to a distant exchange. Most of the exchanges in the world are connected to each other, forming the public switched telephone network (PSTN). By the end of the 20th century almost all were Stored Program Control exchanges.

After the middle 20th century fax and data became important secondary users of the network created to carry voices, and late in the century parts of the network were upgraded with ISDN and DSL to improve handling of such traffic.

Digital telephony is the use of digital technology in the provision of telephone services and systems. Almost all telephone calls are provided this way, but sometimes the term is restricted to cases in which the last mile is digital, or where the conversion between digital and analog signals takes place inside the telephone. Telephony was digitized to cut the cost and improve the quality of voice services, but digital telephony was then found useful for new network services (ISDN) to transfer data speedily over telephone lines.

Voice over Internet Protocol (VoIP) is a general term for a family of transmission technologies for delivery of voice communications over IP networks such as the Internet or other packet-switched networks. Other terms frequently encountered and synonymous with VOIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, and broadband phone.

Internet telephony refers to communications services — voice, facsimile, and/or voice-messaging applications — that are transported via the Internet, rather than the public switched telephone network (PSTN). The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet; the process is reversed at the receiving end.  It is important to note that Voice over the Internet does not allow for Quality of Service (QoS), which in a commercial VoIP deployment is an extremely important factor.  As an example Vonage is a Voice over Internet offering.  Sound quality is unpredictable because the internet quality is not guaranteed by a Service Level Agreement (SLA).   Businesses and organizations requiring reliability should choose circuits that provide SLA’s for network uptime, latency, and availability.  All of these are not guaranteed over the Internet.

VOIP systems employ session control protocols to control the set-up and tear-down of calls as well as audio codecs which encode speech allowing transmission over an IP network as digital audio via an audio stream. Codec use is varied between different implementations of VOIP (and often a range of codecs are used); some implementations rely on narrowband and compressed speech, while others support high fidelity stereo codecs.

Because of the bandwidth efficiency and low costs that VOIP technology can provide, businesses are gradually beginning to migrate from traditional copper-wire telephone systems to VOIP systems to reduce their monthly phone costs.

VOIP solutions aimed at businesses have evolved into “unified communications” services that treat all communications—phone calls, faxes, voice mail, e-mail, Web conferences and more—as discrete units that can all be delivered via any means and to any handset, including cellphones.

VOIP runs both voice and data communications over a single network, which can significantly reduce infrastructure costs.  Again, it is important to note the difference between broadband access and internet access.  VOIP quality is only assured on access circuits that provide a Service Level Agreement (SLA) for network uptime, latency, and availability.

Call Agabar at 800-503-6384 for more information on the technologies that best fit your business, and your budget.