Instructions

266
Fig. 3.54: Circuit 54: Light
sensitive switch with solar
cell
Fig. 3.55: Circuit 55: Light
sensitive switch phototran-
sistor
Circuit 54: The solar cell delivers no current while it is dark, T1 and T2 are blocked. LED1 remains dark. The
solar cell converts light into electricity, which in return puts T1 and T2 in the conductive state and LED1 turns
on.
Circuit 55: The functioning principle is described on page 265.