An electronic private automatic branch exchange or EPABX is used by most businesses. These are systems which provide connectivity between members of the same organization as well as to entities outside the organization.
In the absence of an EPABX, each member of an organization required a separate telephone number given by a telephone services provider. This made internal communication expensive as the telephone service provider's network had to be used. With an EPABX, internal numbers are routed through the system and do not need the telephone service provider's infrastructure. Numbers are also shorter, making them easier to remember and dial.
The EPABX also has several external connections that allow communication outside the organization. The EPABX can automatically link the external caller to the appropriate internal number. Modern EPABX provide many additional services like call waiting, conference calls, call metering, welcome calls, etc.
It has proved to be a very valuable tool in providing inexpensive communication options within organizations as well as improved communication options outside the organization.