Questions: Digital advertising has been revolutionized by Apple's introduction of smartphones

The answer is smartphones.

Transmitters are devices that send signals, but they are not directly related to the revolution in digital advertising. They are more relevant to broadcasting and communication technologies.

Smartphones have significantly revolutionized digital advertising by providing a platform for mobile ads, app-based advertising, and location-based services. The widespread use of smartphones has allowed advertisers to reach consumers directly and interactively, making it a pivotal development in digital marketing.

Pagers were used primarily for simple text messaging and alerts before the advent of smartphones. They did not have the capability to support digital advertising in the way smartphones do.

While computers have played a crucial role in the development of digital advertising, the question specifically highlights Apple's introduction, which is more closely associated with the impact of smartphones, particularly with the launch of the iPhone.