Anyone can explain this website circuit to me?

Question

http://www.electronics-lab.com/projects/test/007/index.html
On positive of input, what use for the chooice of different path of resistor?
On negative of input, what use for the adjustable resistor ?
Can explain whole circuit to me?

Answer 1

The switch switches between voltage ranges. The potentiometer connected to the (-) terminal is used to calibrate the DVM. The +5V and -5V are the voltages which must be supplied in order for the IC's to work properly. The 7107 chip digitizes the voltage difference between pins 31 and 30 and outputs 7-segment codes to the display chips.