The SCS.4DJ is a "Digital DJ Mixstation" made by Stanton Magnetics. It's a little standalone workstation unit with a "Coldfire" ARM (ARM10TDMI?) board in it that runs Linux (2.6.14?) and a custom set of DJ software. The unit seems to have been engineered, both hardware and software, by a company called IVL Audio. The current equivalent product, functionality-wise, would be something like the Pioneer XDJ-RX.
I purchased one of these at clearance prices in 2015. It is both one of the worst and best pieces of DJ equipment I've ever used.
Worst because it's incredibly cheaply made. The control surface itself - the buttons, knobs & sliders - require a very light touch to keep from breaking. The mixer section of mine lasted a year before it started to bleed sound. The computer in the device is underpowered. Even the jacks seem flimsy.
Which is a shame, because the SCS.4DJ does something truly great: it plays two mp3 files simultaneously, through seperate outputs, with pitch and transport control, in a small and lightweight package. I run one "deck" on the SCS.4DJ out the headphone output and the other out the main, with both plugged into my DJ mixer. And there it becomes one of the best: feed it good data, use fast USB drives, handle it carefully and it'll run all night no problem.
The dj software the device runs seems to be called, appropriately, "djapp". It uses GTK2 for its UI and runs Xfbdev(1) to display graphics. It keeps its database in SQLite 3.x format. For it to operate smoothly, feed it good data. I've tried both FLAC and MP3 files, and FLAC has always caused problems. (I suspect because my USB media devices don't have the throughput to stream that much data). I've never had any issues with MP3 files I've encoded myself with LAME.
Maybe I'm being a little unfair with respect to the hardware. As DJWorx noted in their review, the jogwheels are very good. They easily make up for the lack of resolution available with the pitch slider. And while the device always feels like it wants to break, it has not done so yet. Just... don't press anything too hard.
I plan to write a companion to this post about Quickgrid - what it is, how it works, and how to re-implement it using bourne shell, WINE, and parts of the Quickgrid package. That post will come once I clean up my script.
Some of the information in this post is based on the blog post Stanton SCS.4DJ - Under The Hood by Kris Sum at Switch Systems. The rest I gleaned myself from running strings(1) against binaries packed in the SCS.4DJ software update. If my SCS4 ever becomes unusable for DJing, or if I pick up a second one, I'll try to continue Kris' line of exploration (network connectivity, SSH).
So yeah. Apologies if that rambled a bit. I don't recommend this thing to other DJs, as it's too cheaply made and a bit too particular about its data. But if you're a Linux/Unix person this thing is fascinating.