|When one doesn't touch key, the intake valve (1) in the touch box (small pallet box) stays closed. As the intake valve is always connected with the exhaust valve (2), the air goes out of the pneumatic lever (3) this moment. While the pneumatic lever stays deflated, the corresponding pallet is closed.|
|When one touches a key, the intake
valve (1) is pulled to open, and it introduces
air from the touch box to the pneumatic lever. In this
moment, the exhaust valve (2) keeps
closed. The accumulated air inflates the pneumatic
lever (3) which pull and open the pallet to
provide air toward the speaking pipes.
The wind pressure inside of the touch box is around 110mm (high), but the intake valve is much smaller than the pallet. This results in a light touch of the keyboard.
A Barker lever corresponds to one proper note of one proper keyboard. So one needs 56 levers to an organ with one manual keyboard of 56 notes for example. If the instrument is big enough to have plural keyboards, one may multiply the number of notes by the number of keyboards to count the nomber of levers needed.
The Barker lever is quite efficient and reliable
however, it has two defects to improve :
|-||a considerable delay of the pallet action (this seems not very important) caused by waiting for the inflation of the pneumatic lever|
|-||a slow return of the pallet action (this seems important) caused by waiting for the slow deflation of the above-mentioned lever due to the smaller exhaust valve than intake valve necessary to realize a confortable key touch|
|Barker himself, Cavaille-Coll and many other organ builders tried to improve these defects and got a certain satisfaction.|