Why Do Calculators have a Headphone Jack?

On nearly every Texas Instruments graphing calculator, there's a small "headphone" jack along the top. While the port wasn't originally designed for audio, there are some pretty interesting external hardware hacks that can be done through this port. Download the Propeller Code here: https://drive.google.com/open?id=11aTLj7te-MvK1f1cko7KfR1bLJtSMCt6 Other Software Used: TruSound v1.0 - Brian Coventry https://www.ticalc.org/archives/files/fileinfo/433/43319.html (8:50) For More Inforation about the Ti Link Protocol: http://merthsoft.com/linkguide/ Music Used: Late - Topher Mohr and Alex Elena (0:00) No Good Right - Freedom Trail Studio (3:00) Tiptoe Out the Back - Dan Lebowitz (4:09) Birds - Silent Partner (7:57) I've Been Delayed -TAS 1000 (8:50) Clips in Order of Appearance: TI-Robot test - https://www.youtube.com/watch?v=KsX-GBiW9dY (4:09) TI calc wireless - https://www.youtube.com/watch?v=lbqcD5elNM4 (7:22) Graphing Calc Hacked with Touch Screen - https://www.youtube.com/watch?v=pyWIJFLbJZ0 (7:30) Gossamer 1.0: Web Browsing on your Calculator - https://www.youtube.com/watch?v=A9PCf2B7lzA (7:45)