Cool stuff. Thanks for this link, Mark. This answers a long-standing question I've had: How did they accomplish transcontinental telephone service before the use of vacuum tubes? Apparently Western Electric made carbon microphone amplifiers as shown here. Another interesting application of the carbon technology was as one of the first modulators for amplitude modulation of radio carriers in the very first days of radio voice communication. Powerful vacuum tube amps were not yet available, so they used a carbon pile connected to a voice tube as a modulator to vary the plate voltage and/or current on the RF oscillator or even the output of a tuned spark gap transmitter or RF rotary alternator. Crude, and it also got pretty hot carrying all that oscillator power, but that was all they had for awhile. Greg Bogantz ----- Original Message ----- From: "mark lynch" <markelynch at earthlink.net> To: "Antique Phonograph List" <phono-l at oldcrank.org> Sent: Friday, January 25, 2008 5:41 PM Subject: [Phono-L] Museum of Retro Technology Website > > > Here's an interesting site about early Technology you may enjoy. Check the > section under Communications for a few gems: > > > > http://www.dself.dsl.pipex.com/MUSEUM/museum.htm > > > Mark > _______________________________________________ > Phono-L mailing list > http://phono-l.oldcrank.org