The Care and Feeding of ISDN4BSD
5.4.2 The Memory Address	5.4 Kernel Configuration for	5.4.4 The isic Driver

5.4.3 The Interrupt Number

On the ISA bus, the following interrupts (IRQ²) are available for use by an add-on card:

IRQ	normally used by	may be used by us
0	timer/counter	no
1	keyboard	no
2	interrupt controller	no
3	com2	if free, yes
4	com1	if free, yes
5	lpt2	if free, yes
6	floppy controller	no
7	lpt1	not available for Teles S0/16
8	real time clock	no
9	unassigned	if free, yes
10	unassigned	if free, yes
11	unassigned	if free, yes
12	ps/2 mouse	not recommended
13	floating point coprocessor	no
14	IDE hard disk controller	not available for Teles S0/16
15	unassigned	if free, yes

Again, for our example, lets assume you don't have a second printer adapter or anything else which might already use IRQ 5 installed, so we will use it for the Teles S0/16.