A telephone switching center (central office) that does not connect directly to the customer. It connects offices in the same network or between networks, but always deals with trunks rather than customer lines. After Divestiture, most Class 4 tandem offices moved to AT&T, while Class 5 local tandem offices stayed with the RBOCs.
RBOCs installed new tandem offices to handle intraLATA toll calls and provide access to the interLATA toll carriers. Tandem offices and end offices are generally located in the same facility, and may even be serviced by the same switch. See LATA
, tandem switch
and end office switch
Tandem Offices and End Offices
The PSTN is made up of local exchange carriers (LECs) and interexchange carriers (IXCs) that are governed by LATA boundaries. Note that a tandem office carries traffic between end offices and does not link to the customers themselves. Also note that IXC 2 does not have POPs in LATAs 1 and 2 and must have a reselling agreement with IXC 1 in order to gain access to those areas.