External switches and LEDs
Power LED and keylock (KEY LOCK)
You can connect an LED to indicate when the CPU card is on. Pin 1 of KEY LOCK supplies power to the LED; Pin 3 is the ground.
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. The pin assignments appear in the following table:
Power LED and keylock (KEY LOCK)
Pin Function
1LED Power (+5 V)
2No Connector
3Ground
4Keyboard lock
5Ground
External speaker (EXT SPK)
The CPU card has its own buzzer. You can disable the internal buzzer and connect an external speaker to EXT SPK. Enabling the external speaker automatically disables the internal buzzer.
External speaker (EXT SPK)
Pin Function
1Vcc
2Speaker output
3Buzzer in
4Speaker output
30