Ducati ST4S Owner's Manual page 144

Rh switch (fig. 22 )
1) Button = emergency flashers
Press it to simultaneously activate all turn indicators.
Press button again to disconnect the flashers.
2) ENGINE KILL switch, two positions:
position (RUN) = run;
position (OFF) = engine stop.
E Warning
This switch is mainly intended for use in emergency
cases when you need to stop the engine quickly. After
stopping the engine, return the switch to the position
to enable starting.
Important
Stopping the engine using switch (2) when riding
with lights on and leaving the ignition key in the ON
position, may run the battery flat as the lights will remain
on.
3) Button = engine start
34
2
1
3
4
fig. 22