What does the module do? It is able to show the current address and data on a little screen. In addition it has leds for M1, Mreq, RD, WR, and Iorq. It has been tested works with systems from Steve Cousins and myself (Rotten Snow).
The kit came the parts rattling around in a little cardboard box. The seller has genrously added extra LEDs and resistors. The module came with no documentation. 90% of the assembly is obvious indicated by the silk screen. I had to refer to the pictures and schematic presented on here on Tindie for final assembly. I used about 1 hour assembling the module. I made some errrors assembling the kit, but after fixing these it worked.
Is it useful? The LEDS are not that useful but a nice touch. I would have inverted the signals. The little screen isvery nice and could possible be useful for troubleshooting purposes, but I have not tested this.
To conclude, it may not be useful but it makes your system looking more impressive. Recomended.
So happy this things exists. There are very few commercially available midi thru boxes, let alone ones that support this many ports. Picked it up a few weeks ago and it does exactly what it needs to - split one midi signal to 20 outbound channels.