The DZ-1008 relay is recommended to switch the powered rails for longer switches and stuff like the double-slip switch, it switches center track power to the appropriate rail to minimize the amount of space between the rollers being able to be on a powered rail. That function works fine, but sadly it's not really a complete solution. When you have short motorized units of almost any kind, and equally vexing problem is losing power to the wheels, the switching of center roller power does nothing for this issue. With the standard recommended installation, the unpowered rails are just left floating, which obviously doesn't help the wheels maintain power.
In looking at the issue, it's clear that in order to actually power the proper rails for the switch position AND also ground the unpowered ones, it will require more contacts than the DZ-1008 has available. What's needed is a relay module that has two sets of contacts so that both the center roller power and the outside rail power can be managed.
So, I'm setting about righting that wrong with this little project. This is a relay module that has two Form-C sets of contacts to allow switching both the power and ground rails. While I was at it, I made it a little more flexible so I could possibly use it in other applications. It accepts AC power from 12-18 VAC, and input triggers from around 2 volts AC/DC and up to fire the relay. Hopefully, this will be the "silver bullet" that will allow all my small motorized units to finally make a full trip around the layout through the longer curved switches and the double-slip switches. 
The module is 1" x 1.05" and about .6" high, similar in size to the DZ-1008 relay package.
