You should answer black or white. If the answer is black, they should color in the square on their copy. If the answer is white, they should leave the square blank. The fax is completed when all the squares have been either colored or left blank. At this point, all the children should have a facsimile of your picture.
Fax is short for facsimile which means a copy or reproduction.
The sensor switches a signal on or off according to whether a light beam is reflected by white sections or absorbed by black sections. This information is then sent over wires or cables to the receiving machine. The receiving machine decodes the signals using toner or ink to mark the sections that are black. Compare the children s pencil to the toner and their eyes to the sensors.