Ignition retard knock sensor.

[Dave Williams]

-> I have schematic of orig Carter knock eliminator.  Understand that
-> each engine has unique acoustic profile that may require filtering to
-> be effective.

 I've used the Carter boxes on several small block Chevys.  None of them
had any problem differentiating knock from other noise.

 As far as I can tell the EKE is more concerned about amplitude than
frequency.

 Very simple analog devices, but quite effective.