S-COM 6K Owner's Manual page 192

NOTE: The most recent firmware version for the 6K is called V2.1. One
command was added to the firmware in this version:
Hook flash (PW) 63 16 1 *
This command causes the phone line, if engaged, to go on-hook momentarily.
This is similar to someone pressing and releasing the hookswitch button on a
telephone.
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6K V2.0 12-14-01