Final answer:
TTYs utilize the Baudot code and binary signaling, which is a digital method of communication allowing for clear transmission and more efficient use of frequency ranges.
Step-by-step explanation:
TTYs, which stand for teletypewriters, are devices used for communication by people who are deaf or have hearing or speech impairments. They use a character encoding scheme called the Baudot code, which represents characters using a series of five bits. Given the options presented, the Baudot code pairs with binary signaling, as it operates using a binary system of ones and zeros. This method of digital communication ensures that even when a signal is weak, data transmission can remain clear. It also enables the use of computer algorithms to compress digital data, allowing for the efficient transmission of more data within each frequency range. This is akin to how cell phone, television voice, and video images, as well as computer data, are transmitted more efficiently.