词汇	number-unobtainable tone
释义	number-unobtainable tone 电话空号音
随便看	central command central command and control system central command chief army general central command decoder Central Command headquarters Central Command Network central command post Central commerce district central commercial district Central Commission for Discipline Inspection Central Committee central-committee central committee of the CCP central communication command central communication controller Central Communication Region central communications controller Central Communications Facility Central Communications Region central communication system Central Community College-Hastings Campus Central Community College-Platte Campus central compartment central competence central competitive force