From: johnl@iecc.com   
      
   >Would you know the specific code of this device and when it entered service?   
      
   FDM goes way, way back.  Bell's C-carrier put three channels on one circuit in   
   1911.   
   L-Carrier was developed in the 1930s and put 600 channels in a coax.   
      
   Bell was working on the harmonic telegraph, FDM telegraphy, in 1876 when he   
   suddenly invented the telephone the same day Elisha Gray did.   
      
   >  As menitoned, the older concentrator simply switched users around a smaller   
   >number of trunks with the potential of blocking.   
      
   That's much newer.  The oldest use of that I know is TASI, used in the 1960s on   
   long distance undersea cables.   
      
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   Regards,   
   John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies",   
   Please consider the environment before reading this e-mail. http://jl.ly   
      
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