Professor Stephen Hawking addresses Headway conference

The transcript describes the journey of using assistive technology for communication. Initially, a computer expert from California provided a program to help select words using a switch. Later, a more advanced program by Intel, controlled by a sensor, was adopted. The user sends typed messages to a speech synthesizer, which produces a recognizable voice. Despite technological advancements, the user remains attached to the original synthesized voice.

What technology does the author use to send messages?

Why does the author not intend to change the voice of the synthesizer?