Here is some more information: https://en.wikipedia.org/wiki/All_Red_Line

And one of the old cable huts still exists: https://en.wikipedia.org/wiki/Pacific_Cable_Station

When visiting Ayers Rock in Australia I stayed in Alice Springs. While I was there I learnt that Alice Springs exists because it was a repeater station for a telegraph line that stretched from Southern Australia all the way to London. There would be people listening to morse code, and tapping it out again to the next repeater station. Blew my mind that there was a wire that went all the way to London from Australia!

Fun facts, the subsea telegraph network cables coating were made from Gutta Percha [1].

Unlike normal rubber, it is a type of thermoplastic and it's a popular organic plastic before the petroleum based modern plastic become pervasive [2].

[1] The legacy of undersea cables:

https://blog.sciencemuseumgroup.org.uk/the-legacy-of-underse...

[2] Gutta-percha:

https://en.wikipedia.org/wiki/Gutta-percha

An interesting book on the subject of telegraph networks is The Victorian Internet by Tom Standage [1]. As well as the technical and commercial drivers, it also describes how the telegraph forced people to confront concepts like simultaneity, information being distinct from its physical medium, privacy, early approaches to encryption, etc. A fascinating book.

[1] https://en.wikipedia.org/wiki/The_Victorian_Internet

Is the latency the same now as it was for the signal itself? Obviously the throughput is rather different.