To extend the memory capacity
To control demultiplexing the address and data bus
To distinguish between external RAM and PROM
To initialize parallel port
LDR
RTD
Potentiometer
Optocoupler
Interference
Total Internal Reflection
Diffraction
Photo Electric Effect
Microwave communication
Satellite Communication
Terrestrial Communication
Optical Fiber Communication
0 V
0.7 V
10 V
0.2 V