If you have a spare T/R & line port,
loop them together (two wire jumper/phone cord)
set up the T/R as a "hotphone" with first speed dial = 0
add the line to the 4406, set it as first in auto line select
Keep in mind, I don't think you can remove all system access buttons, so the phone can still be used to dial other extensions, you'll definitely want to enable outward restrict.
when you lift the handset, it'll activate the T/R hotphone, calling the operator.
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