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In telephony, the term on-hook has the following meanings: # The condition that exists when a telephone or other user instrument is not in use, ''i.e.'', when idle waiting for a call. Note: on-hook originally referred to the storage of an idle telephone receiver, ''i.e.'', separate earpiece, on a switchhook. The weight of the receiver depresses the spring-loaded switchhook thereby disconnecting the idle instrument (except its bell) from the telephone line. # One of two possible signaling states, such as tone or no tone, or ground connection versus battery connection. Note: if on-hook pertains to one state, off-hook pertains to the other. # The idle state, ''i.e.'', an open loop of a subscriber line or PBX user loop. # An operating state of a telecommunication circuit in which transmission is disabled and a high impedance, or "open circuit", is presented to the link by the end instrument(s). Note: during the on-hook condition, the link is responsive to ringing signals. The act of ''going on-hook'' is also referred to as ''releasing the line'' or ''channel'', and may initiate the process of clearing. ==See also== * disconnect supervision 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「On-hook」の詳細全文を読む スポンサード リンク
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