The Apollo Pulse Board is necessary to interface between an Apollo and a machine that's using a pulse interface. It's a simple input-output system where a payment on the terminal generates a pulse on an output pin. This output can be connected to a machine, a door or whatever you want to control. In many cases it's also important to temporarily block payments. For example, you might not want your customers to pay when the machine is active. For that we offer an optional input pin.