Siemens optiPoint 420 standard - Open Listening in the Room During a Call; Off-Hook Dialing; On-Hook Dialing

Introduction
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Keypad
The optiPoint 410/420 advance S V6.0 keypad features digits, letters and
some special characters. Depending on the selected input mode, you can
key in letters and special characters by pressing the relevant key as often
as necessary until the required character appears on the display.
Examples of letter inputs are the password, the user name, or FTP down-
load files and file paths respectively.
For example, if you want to enter the letter "R", press "7" three times as "R"
is at the third position. For the letter "U", press "8" twice.