H. Wabnig wrote:
On Mon, 11 Jun 2007 01:24:01 GMT, Angelo Campanella
wrote:
And here's the Wikipedia reference:
http://en.wikipedia.org/wiki/Antonio_Meucci
requires coils of really THIN copper wire.
Any historian ever looked at the manufacturers of insulated wires?
At what point in time did the wires become available?
Meucci was a dedicated tinkerer, following Galileo's recommendation to
"try and try again".
After about 1854, he used commercially available telegraph coils with
pole pieces as transducers and iron telegraph wire for transmission. For
long distance work, he did have a large bobbin of telegraph wire, widely
available by then. Most telegraph wire was uncoated galvanized iron
wire, as it was most easily available in bulk.
Through more tinkering, he found that better sound quality occurred for
wire coated with a graphite inorganic salt slurry. He then tried smaller
wires laid in parallel in place of a single telegraph wire to discover
that the high frequency speech currents purveyed better. He wrapped
relatively thin iron and copper wire with cotton.
This action prompts Basilio Catania, author of most of the modern
research into Meucci's life and times, to conclude that Meucci has
discovered the now well known "skin effect".
As often as not during 1854-1870 inclusive, he used the ends of wire
from a large spool of insulated iron wire for telephone tests and
demonstrations for his Staten Island friends and neighbors. It was
during those activities that he discovered that the received speech
sound was stronger with that bobbin of indulated telegraph wire in
place, as opposed to direct connection. It was so superior that he did
not need to use battery current to energize the transceiver magnet. The
residual magnetism of the iron transducer core was sufficient. This
action was in reality due to the better audio frequency impedance match
offered by the distance bobbin, aka "inductive loading" of a
transmission line.
Basilio Catania, circa 1990, used this specific result to independently
conclude that Meucci was THE authentic inventor of the telephone.
As you may recall Alexander Graham Bell took out the first related
patent on the transmitting speech over a telegraph line in 1876. In
reality, speech transmission was added as an afterthought to a patent
primarily aimed at simultaneous transmission of several telegraph
messages using ac signal of differing frequency for each. The comment
was added that "currents modulated by speech were also possible".
Angelo Campanella