[Yaesu] CW button/dial

[Harold Mandel]

On the Yaesu FT-1000 there is
a CW SPEED dial on the lowest 
right-hand side of the front panel.
 
This controls the Keyer speed.
 
This button pushes in and latches,
and vice-versa, unlatches and
springs back out.
 
There is electrical circuitry attached 
to the switch part and electrical
circuitry attached to the pot part.
 
What does this pushbutton function do?
 
Hal Mandel
W4HBM