ON HOOK

1. In telephony , the condition that exists when an operational telephone , or other user instrument, is not in use. ( 188 ) Note: On-hook originally referred to the storage of an idle telephone receiver, i.e., separate earpiece, on a hook that extended from a vertical post that supported the microphone also. The hook was mechanically connected to a switch that automatically disconnected the idle telephone from the network . 2. One of two possible signaling states, such as tone or no tone, or ground connection versus battery connection. ( 188 ) Note: If on-hook pertains to one state, off-hook pertains to the other. 3. The idle state , i.e. , open loop , of a subscriber or PBX user loop. ( 188 ) 4. An operating state of a communications link in which data transmission is disabled and a high- impedance , i.e., 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.