You probably need to contact DTVS in order to find out more information about latest firmware
The DTVS-1B doesn't have a USB slot , so even if there was a firmware upgrade how would you apply it ?
The DTVS-1B firmware can only be upgraded via OTA (Over the air) when and if its being broadcast.
According to the User Guide it has an RS232 socket on the back panel for software update.
Really old stuff as most new PCs don't have RS232 Com Ports any more so you'd need a USB to RS232 interface cable for updating.
doing it via rs232 is really easy,just need the file and loader