The document traces the evolution of telephones over time, from wall-mounted telephones to portable cell phones. It notes several milestones, such as Alexander Graham Bell's invention of the telephone in the 1870s, the introduction of the first portable handset by Motorola in 1984. It discusses how cell phones have increasingly integrated additional functions beyond calling, such as texting, internet access, cameras, and GPS. The document also analyzes how cell phone usage differs between social classes, with those of higher income and education more likely to adopt newer cell phone models and technologies.