发明授权
- 专利标题: Selective paging and intercommunication system
- 专利标题(中): 选择性寻呼和互通系统
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申请号: US152212申请日: 1980-05-21
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公开(公告)号: US4377726A公开(公告)日: 1983-03-22
- 发明人: William H. Schiffbauer , Richard A. Watson
- 申请人: William H. Schiffbauer , Richard A. Watson
- 申请人地址: DC Washington
- 专利权人: The United States of America as represented by the Secretary of the Interior
- 当前专利权人: The United States of America as represented by the Secretary of the Interior
- 当前专利权人地址: DC Washington
- 主分类号: H04M9/00
- IPC分类号: H04M9/00 ; H04M13/00
摘要:
A battery powered paging and intercommunication system for application in a mine or other environment where it is necessary to conserve battery power comprises a plurality of transceivers electrically coupled to a common pair of signal lines. Each of the transceivers includes a push-to-talk switch for applying voice signals onto the lines as well as a push-to-page switch that amplifies received voice signals for reproduction through a loudspeaker. Each transceiver also includes dual tone multifrequency (DTMF) encoder and decoder circuitry for addressing a preselected transceiver on the lines for paging. A timer circuit within the transceiver limits the period of time the transceiver limits the period of time the transceiver is in the paging mode to reduce battery consumption. As a system check during paging, the called transceiver generates "beep-back" signals on the lines indicating to the calling transceiver that it is receiving paging signals. A second timer circuit controls a light flasher at the called transceiver to serve as a call back signal.
公开/授权文献
- US5557553A Computer assisted time study system 公开/授权日:1996-09-17
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