MIT Tech Review | Starlink signals can be reverse-engineered to work like GPS--whether SpaceX likes it or not, 21 Oct

[...]
 For the past two years, his team at UT Austin's Radionavigation Lab has been reverse-engineering signals sent from thousands of Starlink internet satellites in low Earth orbit to ground-based receivers. Now Humphreys says his team has cracked the problem, and he believes that regular beacon binary data signals signals from the constellation, designed to help receivers connect with the satellites, could form the basis of a useful navigation system. Crucially, this could be done without any help from SpaceX at all.
[...]
Humphreys quickly realized that Starlink relies on a technology called orthogonal frequency-division multiplexing (OFDM). OFDM is an efficient method of encoding digital data transmissions, originally developed at Bell Labs in the 1960s and now used in Wi-Fi[,] and 5G. "OFDM is all the rage," says Mark Psiaki, a GPS expert and aerospace professor at Virginia Tech. "It's a way to pack the most bits per second into a given bandwidth."

The UT Austin researchers did not try to break Starlink's encryption or access any user data coming down from satellites. Instead, they sought out synchronization sequences--predictable, repeating signals beamed down by the satellites in orbit to help receivers coordinate with them. Not only did Humphreys find such sequences, but "we were pleasantly surprised to find that they [had] more synchronization sequences than is strictly required," he says.
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reference
What is adornment?
What is speech?
What is cave painting?
What is cunieform?
What is an alphabet
What is a telegraph?
"A telegraph is a communication system that sends information by making and breaking an electrical connection."

What is morse code?
-- --- •-• ••• • -•-• --- -•• •
What is binary code?
0100 0011 0100 0001 0101 0100

What is a modem
"The earliest devices that satisfy the definition of a modem may be the multiplexers used by news wire services in the 1920 1840s."
What is a telephone?
"the equipment necessary to convert sound to electrical signals and back"

Dretske, F., Knowledge and the Flow of Information