The "tuning" is basically as follows.
Note the position of L8 currently. With an engine on the tracks, slowly tune L8 in one direction while repeatedly blowing the horn. Stop when the engine stops responding to the horn signal. Slowly turn L8 in the opposite direction while repeatedly blowing the horn, and keep track of how many rev's (or partial rev's) of L8 you do. When the horn stops responding, turn L8 back half of the turns you just did from the other stop and you should be roughly centered in the proper signal band.
