Synthesized answer
The provided passages do not contain enough information to explain the key concepts of the electrical telegraph in my own words. The title mentions Samuel Thomas von Sömmerring's "Der" elektrische Telegraph as a German invention [26], but it does not detail how the telegraph works or its fundamental principles.
To explain the key concepts, I would need passages that describe the operational mechanism of the telegraph, such as how electrical signals are transmitted, interpreted, and received. Information regarding the components of the telegraph and their functions would also be necessary.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: “Der” elektrische Telegraph als deutsche Erfindung Samuel Thomas von Soemmerring's by Samuel Thomas “von” Sömmerring Pages: 26