Lucent Technologies 5 manual Background

MERLIN LEGEND Communications System Release 5.0	Issue 1
System Manager’s Guide 555-650-118	June 1997

2About the System

Background	Page 2-2
Background	2

Alexander Graham Bell and his assistant, Thomas A. Watson, demonstrated the first working model of a telephone on March 10, 1876. Bell made the call from a transmitter in one room to a receiver a few rooms away.

The first telephone installations were set up like that first call, as direct connections between one telephone and another. When more and more telephones were installed, it quickly became impractical to have every phone connected directly to every other phone. Thus, the concept of switching developed, that is, all telephones connected physically to all other telephones, but each telephone could make the electrical cross-connection between itself and another phone so that the caller was connected to the called party.

Again, as more and more telephones and lines were installed, it became impractical to have each telephone perform this switching function, so all lines from all phones were brought into a common place, called a central office (CO) or exchange (see Figure 2–1) where human operators switched calls at switchboards. This 2-way connection between the telephone and the CO was (and still is) called the local loop. Eventually, more and more COs were created and interconnected, until the current global telephone network evolved (see Figure 2–2).

As geographic areas expanded and the global telephone network evolved, and as technological advances became available, switches also evolved and are now fully automatic and controlled by computers.

There are now also private switches that, rather than being located at the telephone company’s CO, are located on a company’s premises. These systems, called private branch exchanges (PBXs), made sense because most of a business’ calls are between telephones on site within the company.

The MERLIN LEGEND Communications System includes such a switch, located on a company’s premises, that offers access to even more powerful telephone network applications and services. It can operate as a PBX (Hybrid/PBX mode) or can be set up to operate in one of two other modes that define how the system works. The system can also use state-of-the-art telephone equipment.

The next sections briefly describe the evolution of telephone equipment and

switching. For more information, see Appendix B, ‘About‘ Telecommunications’’.