Electrical signals can be converted into light signals for transmission purposes. This experiment demonstrates the basic principle of this process, not having any practical value. An LED converts 20 Hz pulses to light pulses and transmits them. An LDR receives them and converts back into electrical pulses.
Make the connections as shown in the figure. Place the LED facing the LDR. The voltage across the LDR is plotted. Tapping on the SEN icon displays the frequency and duty-cycle of the received signal.