67IndexOOne Number Servicecallback .................................................... 26do not disturb .......................................... 56overview of functions ............................ 64second call (call waiting) ....................... 34Open listening ............................................ 15Operating principle .................................... 13Operational elements ................................ 10PParallel call (overview of functions) ......... 64Phoneoperating .................................................. 13Pickup callteam ......................................................... 29Product designation ..................................... 9RRedialing a numberlast number dialed ................................. 18saved number ......................................... 18Relocating .................................................... 62Repdial keys ................................................ 17Ring tone ..................................................... 63Ring volume ................................................ 63SSecond call .................................................. 33Serial number ............................................... 9Shift key ....................................................... 35Speed dialingdialing ....................................................... 31TTelephone maintenance ........................... 65Three-party conference ............................. 36Toggle/Connect .......................................... 20Tone dialing ................................................. 37Transferring (call) ........................................ 21Troubleshooting ......................................... 65Two-way intercom system ....................... 41UUser support ................................................. 8VVolumekeys .......................................................... 11set ............................................................. 17