Simplify the following text for a Grade 9 native English-speaking person.
Original: In 1937 Shannon went on to write a master 's thesis at the Massachusetts Institute of Technology , in which he showed how Boolean algebra could optimize the design of systems of electromechanical relays , then used in telephone routing switches .
Simplified: In his doctoral thesis , Shannon showed that boolean algebra was useful . It could simplify the design of electric switches and relays ( like those that were used in the telephone switchboards of the time ) .