"Half Stop" is a changer action which allows to obtain 2 notes on a lever course in 2 steps. In general this action is applied to the lower. You obtain a first alteration with a stop feeling (for exemple a Half tone) and a second alteration by extending the course to the complet course (one more haf tone in general).
The most current exemple is applied to the string 2 on E9 neck wich give a D# open string. First half stop goes to D and second finish the lever course to C#.
The sytem will allow adjustment of the half-stop of the lever to "feel stop" and then setting the final stop.
You can obtain the full stop with different methods.Those examples are for "All pull systems" but some can be applied to other changer (we'll talk about it soon)
1.Half-stop adjustable by a fell-stop system on the lever course:
2.Stop ball system Lozach'/Wiesner-Schild:
This system designed by Jean Yves Lozach' for Wiesner guitars in the 90's is probably the best Half-stop ever made for a pedal steel guitar. A rod in wich a groove is machined make the feel stop when the ball is engaged in the groove. The rod is mooving when the knee is actioned and you can adjust the leght of the rode (and the distance between the rod and the knee to tune your first half). Behind the half stop a screw give more or less course for the rod to tune the full action. The ball is pushed by a spring and you can adjust the spring with a screw (not on pics) to obtain softned or harder feeling.
3.Half stop system with a free lower finger:
figure 2b: Half stop on string 2 and feel stop on string 9 with Allen screw (split tuning screw) used for split adjustement.
4.Half stop using extra finger:
figure 2C: Half stop on string 2 and feel stop on the 11th extra finger (Carter, MSA...)
To harden, screwing the return spring of the extra finger (11th)