Sandmartin Electronic Co. Ltd. DCM4-HD 用户手册

If you want to update the receiver by using a USB 2.0 compatible Stick or such
USB Hard Drive Disk,
please  press  [VOL].  Select  the  Upgrade-file  and  start  by  press  the
[VOL] key.

Note: Do not remove the USB stick or power off during operation, otherwise you
may cause a service issue!