Analog Telephone Networks

The analog telephone network is basically made up of four stages as shown in the following illustration. Exchanges at lower levels in the network hierarchy process calls over a shorter distance and those at higher levels process calls over a longer distance, improving facility efficiency.

Regional Center: RC

The area consisting of several district areas (DAs) is called a regional area (RA). The regional center is installed at the center of the regional area.

District Center: DC

The area consisting of toll areas (TAs) organized somewhat like a single prefecture unit is called a district area (DA). The district center is installed at the center of the district area.

Toll Center: TC

The area consisting of several local service areas (LAs) is called a toll area (TA). The toll center is installed at the center of the toll area.

End Office: EO

The end office is a switching office accommodating subscribers' lines, placed at the lowest level in the network hierarchy.