CRYSTAL PHONOPTICON 
319 
ing out from the rods and cones. The resistances in fig. 21 are 
so chosen that when the white page is illuminated, there may 
be a zero or small electric current through the telephone re- 
ceivers. Then when a dark letter or part of such letter moves 
in front of the lens at focus 6^ there is less light focussed on all 
or part of the row of crystals. The crystals that receive less 
light instantly increase in resistance and so cause a current- to 
flow through the receivers as long as the dark portion of the letter 
remains at the focus of the lens. 
The Discernment of Characters . — As various characters move 
in front of the lens there is a combination of electric currents 
set up in the various telephone receivers. There is also a var- 
ious combination of sequence in which these currents may appear 
depending on the form of the character that passes before the 
lens. Also these electric currents vary in intensity depending 
upon the width of line or part of letter that is in focus. 
The various electric currents may be discerned by the ear 
by having in each circuit individual to each crystal both a tele- 
phone receiver and an interrupter. Each circuit has a frequency 
of interruptions distinct and different from all the other circuits. 
Therefore each circuit produces a different pitch in the ear 
from every other circuit. Then the ear will detect the form of 
a letter on a black page by the order and sequence of the differ- 
ent pitched notes that the ear hears. Also a trained ear will 
Fig. 22. — The Crystal Phonopticon in present state of development, (a) 
Selenium eye with head receivers on the book to the left in the picture, 
(b) Motor with interrupters to the right, (c) Remaining parts are 
auxiliary resistances, wires and battery. 
