The history of telephony is intimately linked to the invention and development of the telephone. The term is used frequently to refer to computer hardware, software, and computer network systems. In this context the technology is referred to as Internet telephony. The first telephones were connected directly in pairs, each user had a separate telephone wired to the locations he might wish to reach. This quickly became inconvenient and unmanageable when people wanted to communicate with more than a few people, the inventions of the telephone exchange provided the solution for establishing telephone connections with any other telephone in service in the local area. Each telephone was connected to the exchange via one wire pair, nearby exchanges in other service areas were connected with trunk lines and long distance service could be established by relaying the calls through multiple exchanges. Initially the switchboards were manually operated by an attendant, a switchboard operator, when a customer cranked a handle on the telephone, it turned on an indicator on the board in front of the operator who would plug the operator headset into that jack and offer service. The caller had to ask for the party by name, later by number. If the called station answered the operator disconnected their headset and completed the station-to-station circuit, trunk calls were made with the assistance of other operators at other exchangers in the network. 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 number of drop wires from all over a district access network to one wire center or telephone exchange. Most of the exchanges in the world are interconnected through a system of larger switching systems, today, telephony uses digital technology in the provisioning of telephone services and systems. This advancement has reduced costs in communication, and improved the quality of voice services, the first implementation of this, ISDN, permitted all data transport from end-to-end speedily over telephone lines. This service was made much less important due to the ability to provide digital services based on the IP protocol. The integration of software and computer systems is a major development in the evolution of the automated office. The term is used in describing the services of call centers. Its also sometimes used to describe the ability to use your personal computer to initiate, CTI is not a new concept and has been used in the past in large telephone networks, but only dedicated call centers could justify the costs of the required equipment installation. Dialed Number Identification Service on a scale is wide enough for its implementation to bring value to business or residential telephone usage
A commercial IP telephone, with keypad, control keys, and screen functions to perform configuration and user features.
Fixed telephone lines per 100 inhabitants 1997–2007