# Switch block 1: interrupt level

The interrupt level corresponding to each switch position is printed on the circuit board next to switch block 1.

Position | Interrupt level | Position | Interrupt level
1 | IRQ 15 | 5 | IRQ 7
2 | IRQ 12 | 6 | IRQ 5
3 | IRQ 11 | 7 (default) | IRQ 3
4 | IRQ 10 | 8 | IRQ 2 or 9

- Use IRQ 7 or lower if you are installing the Smart 16/4 AT Ringnode in an 8-bit expansion slot.

- Select an interrupt level that does not conflict with any other boards or devices that are installed in your computer.

- Some applications, such as the IBM 3270 Emulation Program, do not work with all interrupt levels.

- Several interrupt levels are used for particular purposes and this may also affect your choice. Click here for examples.