IRQ (Interrupt Request Line) sets the unique IRQ number and path for each device by setting a DIP switch. The Interrupt Request Line stops the currently running program and lets the interrupt handler to run. The interrupt handler then determines what processing to perform next. The IRQ (Interrupt Request) can be software IRQ (initiated by software program) or hardware IRQ (sent by a peripheral device). USB Plug and Play prevents the IRQ (Interrupt Request) conflicts.