HI rOy,   
      
      
   On Mon 2012-Jul-30 06:25, Roy Witt (1:387/22) wrote to Richard Webb:   
      
    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.   
      
    RW> I'm not sure this is electronic, large air tank, with a   
    RW> fitting that can be used to pressurize it.  This is one   
    RW> reason I wonder if at one time there wasn't air brakes with   
    RW> hydraulic assist as well as the hydraulic.   
      
   Roy> I was thinking it was a vacuum tank, but you mentioned 'air gage'   
   Roy> which would mean to me that it is a pressurized tank. If you had   
   Roy> mentionedd 'vacuum gage' I wouldn't have to assume anything. If you   
   Roy> can, checking the cab-mounted horns for hoses or wires would give us   
   Roy> an idea of what they are. Or a pull-chain air valve in front of the   
   Roy> driver...   
      
   I'll look, there's the usual pull chain to "honk" the horn   
   of course, will look down around the dash see what I find   
   there next time I go out there.  Right now think I'll get   
   unroasted for a bit here, been hauling in groceries, and   
   thermometer at the bank on the corner says 104 degrees.   
      
   I'll try to remember to go out there snooping tonight see   
   waht I find, because to be honest I'm not sure which this   
   might be.   
      
      
   Regards,   
              Richard   
   ---   
    * Origin:  (1:116/901)