Before order,you should know exactly what is the difference between MDB-RS232 and RS232-MDB:
MDB-RS232 is used to connect the MDB bill acceptor,coin validator,cashless payment device to computer. then you will design the Software that will run in the PC and work as the master main vending controller. For example,you develop the kiosk information machine. then you need to connect the MDB bill acceptor,coin validator to computer,but you don't know how to connect the MDB interface payment device to computer, because computer only has the RS232 port, no MDB port.then you need to order the MDB-RS232 adapter (MDB2PC Adapter ).
RS232-MDB is used to connect the pc to existing vending machine.then you will need to design the Software that will run in the PC and work as the slave cashless payment device.and then you PC will work as a cashless payment device to vending machine. For example,you want to use the PC to give payment credit to existing vending machine, or if you want to make the internet connection to the vending machine and give credit to vending machine remotely, then you need to order the RS232-MDB adapter (PC2MDB adapter ).