* Reply to a message in fidonews.   
      
   On Fri 2012-Jul-27 05:39, Roy Witt (1:387/22) wrote to mark lewis:   
      
    ml> i can't say that i've ever known an air horn to work on a vaccum   
    ml> system... or air brakes, for that matter... everything i've seen has   
    ml> been under pressure...   
      
   RW> Yes, air horns require a compressor, but there are also electronic   
   RW> horns that can wail at 108db that sound like the old air-horn you're   
   RW> talking about.   
      
   I'm not sure this is electronic, large air tank, with a   
   fitting that can be used to pressurize it.  This is one   
   reason I wonder if at one time there wasn't air brakes with   
   hydraulic assist as well as the hydraulic.   
      
   There is a regular electric horn though under the hood, but   
   air horn is atop the cab, at least the "trumpet" part, tank   
   mounted down low, usual configuration as would be seen in   
   your usual Freightliner or Kinworth.   
      
   Regards,   
              Richard   
   ---   
    * Origin:  (1:116/901)