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Chapter 3 Connecting peripherals 19
External switches and indicators
Next you may want to install external switches to monitor and
control your CPU card. These features are completely optional —
install them only if you need them.
Reset switch (J1)
You can connect an external switch to easily reset your computer.
This switch restarts your computer as if you had turned off the
power then turned it back on. Install the switch so that it closes the
two pins of J1.
Power LED and keylock (CN1)
You can connect an LED to indicate when the CPU card is on. Pin
1 of CN1 supplies power to the LED and Pin 3 is the ground. For
help finding CN1 see the figure on page 5.
You can use a switch (or a lock) to disable the keyboard. In this
state the PC will not respond to any input. This is useful if you
don’t want anyone to change or stop a running program. Simply
connect the switch between Pins 4 and 5 of CN1. The pin assign-
ments for CN1 appear in the following table:
Power LED and Keylock (CN1)
Pin Function
1 LED Power (+5 V)
2 No Connection
3 Ground
4 Keyboard lock
5 Ground
Hard disk drive LED (CN2)
You can connect a LED to connector CN2 to indicate when the
HDD is active. Marks on the circuit board indicate LED polarity
(the pin on the left is positive).