| 单词 | Class 2 |
| 释义 | Class 2 In the traditional public switched telephone network (PSTN) hierarchy, a sectional toll center. Class 2 offices served to interconnect Class 3 offices, or primary toll centers, largely for interstate calling within a geographic region of North America. Approximately 67 sectional toll centers existed prior to the breakup of the Bell System. It is doubtful that any remain. See also Bell System, Class 3, and PSTN. 74570c03.qxd 9/11/07 12:19 PM Page 98 |
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