Oki OF5650 User Manual page 50

Device Wizard: Preamble
If you have to dial "9" to get an outside line (or any other digits) you should enter
it here.
If you would like a delay anywhere in this dialing preamble you should enter an
ampersand (&) to give a pause of about one second.
If you are using Unimessage Pro at home and need to dial a code number to
charge the cost of your fax messages to a different account, you could enter the
code number here.
Remember that you can use the "/" character at the start of a fax number in
Unimessage Pro to tell Unimessage Pro to ignore any Preamble you might have
entered.
For example "9&" meaning "dial 9 for an outside line, pause for about 1 second,
then dial the rest of the number."
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