[Milsurplus] Mechanical filters with 128Hz spacing

[MillerKE6F at aol.com]

I believe these filters were used as FDM channel modems in microwave and  
land line carrier systems.  for orderwire channels and fault alarm channels  
that sit under the normal FDM channel modem group that ranges from 60 to 108 
KHz  which is 12 channels with 4 KHz spacing. This is wild guess, of 
course, and they  could be used for other stuff too.  If they are orderwire 
channels the  bandwidth would be approaching 3400-3600 Hz.
 
    Cheers
 
    Bob, KE6F