Engineering and Operations in the Bell System

1ESS 4ESS switching applications AT&T automatic automatic message accounting basic Bell Laboratories Bell operating companies Bell System BOCs busy cable carrier systems centers central office channel bank circuits coaxial coin communications connection cost cross-connect Crossbar crossbar switches customer's data link data sets described developed dial digital carrier digroup discusses economic electronic switching system engineering example facilities network frequency functions input installation interconnection interface interoffice intertoll trunks load loop maintenance mastergroup ment microwave modulation multiplex off-hook on-hook operations systems pairs path percent performance planning processor PSTN pulses radio receiver remote route satellite Section shown in Figure station switching equipment switching network T-carrier tandem telecommunications telephone company terminal equipment time-division tion toll traffic transmission facilities transmitted trunk groups types unit VF channels voice voiceband Western Electric wire