HP 372284-001 - Manual (Page 29)

Firmware Upgrade Utility
4. Slide the Firmware Upgrade Switch to the UPGRADE position.
5. Power on the switch by plugging in one of the KVM cables. The switch front panel LEDs
flash to indicate that it is in Firmware Upgrade mode.
CAUTION: Do not attempt to operate the switch during the firmware upgrade process.
4-2 HP 1x4 USB/PS2 KVM Switch User Guide