[TenTec] Source for Binaural Receiver

[Ralph Matheny K8RYU]

This concept goes back \at least to the 1970's when a 
fellow named Hlidreth (I think) wrote several articles for
Ham Radio describing audio filtering systems.  The idea 
always sounded great but I have only used it a little.
It does help keep one "on the ball" during long sessions.

I think at least one manufacturer has something similar
if not identical in a radio popular today...

Orion latest firmware has feature I think but I have never
tried it out.....

de K8RYU