 The thallium sulphide (Thalofide) cell, developed by Theodore Case in the USA , detected the light reflected from the subject and converted it into a proportional electrical signal.
<fluency>  The thallium sulphide (Thalofide) cell, developed by Theodore Case in the USA , detected the light reflected from the subject and converted it into a proportional electrical signal.
 The thallium sulphide (Thalofide) cell, developed by Theodore Case in the U.S. , detected the light reflected from the subject and converted it into a proportional electrical signal.