| 摘要 |
When replacing an old exchange with a new one, one or more of a small unit (board or magazine) of the old exchange is removed at a time, and replaced by new equipment controlled through a different communications channel than the old equipment This enables reuse of the existing MDF as well as the cabling from the MDF to the old exchange, which saves cost and also eliminates the need for a lot of changes to cabling documentation and support systems for handling cabling information. When upgrading as described, the new line boards can be designed to provide both voice and DSL services, or else can be made smaller or with higher capacity, so that extra space is freed up for placement of DSL equipment. The new equipment is installed in the same place as the old line board, or at least close enough to the correspond |
