The keypad is a vestige of the rotary dial, which itself is an artefact of the switch from human operators to direct-dialling in the1920 s.

 
  • 数字键盘演变自转盘拨号器,而转盘拨号器则是1920年代人工接线员向直接拨号转变的产物。
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  • 深远海浮式风电平台 - deep-sea floating wind power platform
  • 京雄高速公路 - Beijing-Xiongan expressway
  • 农业及相关产业增加值 - the added value of agriculture and related industries
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