基思寻线机的发明，导致自动交换台的成本大幅降低，并首次用于特拉华州的威明顿。
Invention of Keith Line Switch, resulting in enormous reduction in cost of automatic boards. First used at Wilmington, Delaware.
基思寻线机的发明，导致自动交换台的成本大幅降低，并首次用于特拉华州的威明顿。
Invention of Keith Line Switch, resulting in enormous reduction in cost of automatic boards. First used at Wilmington, Delaware.
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