Hi,
I use Mach4 an Ethernet SmoothStepper and my own homemade breakout board.

The breakout board does not really 'do anything', that is to say it does not have logic or other smarts on it, but rather amplifies and buffers both inputs and outputs and
provides convenient screw terminations (or sockets/plugs) to connect to real world hardware. A good breakout board will hopefully provide some protection for the ESS should
you have a wiring sanfu.

The pic I have posted of my BoB. Not all the inputs and outputs are 24V, excepting the differential motor outputs. So my BoB provides the voltage translation from the 5V of the ESS
to 24V of my servos. If you apply more than 5V to an ESS input or output you'll wreck....so don't do it. This is the sort of protection that a BoB offers. It also has a Spindle On/Off relay, a Spindle
PWM output circuit, and a 24VDC output for the Z axis electromagnetic brake. All-in-all you can see I made my BoB to suit my machine.

There are plenty of BoB's ranging from a simple C10 ($23.00) up to an MB3 by CNCRoom. The MB3 ($190) is a three port board with differential motor outputs, a good balance of 24V tolerant inputs and outputs,
with relays for the spindle and a rather clever PWM output circuit. Despite the cost an MB3 is favoured.

Craig