the DQ153 is a controller board for pertec tapes, which were a 
popular (albeit rather proprietary as they were formatted at the factory
and couldnt be reformatted) cartridge tape. Aside from very limtied hack 
value of being turned into somethign else, the baord is pretty useless
these days, as it is not very common to see either a pertec tape or 
drive. 

as for the sigma, i'd never heard of them havign made a SCSI/Qbus
interface, though its entirely possible. The only thing i knew of from them
was a Qbus RLL controller. 
still, if youve found a SCSI/Qbus board, consider yourself lucky!! 

happy hacking!

On Sat, 21 Nov 1998, Stan Pietkiewicz wrote:

> I recently came across a dual-height Dilog DQ153 Qbus card and a card
> with "Sigma Information Systems" near the bottom edge, and "scsi 1.87B"
> hand written on an EPROM chip label. I would guess that the Sigma is a
> scsi controller card, but  I'm puzzled about the Dilog....what is this??
> 
> Any more information about the Sigma would be appreciated as well.....