October 2010
Intermediate to advanced
320 pages
8h 34m
English

Where would we be without amplifiers? The telegraph system was invented in 1844 long before amplifiers existed. The figure below shows an early input key. The signal had to be relayed down the line from each station because it weakened with distance. Imagine our world without amplifiers. It would be a quiet place.
The Parts Bin on the following page has the complete parts list used in Part Four.

Imagine our world without amplifiers. It would be a quiet place.
PARTS BIN ...