Echo DHC-30 - Manual (Page 5)

2-2 Switch function
DHC-3000
SERVICE HINT
5
Circuit protector
Spring
Switch trigger
Safety switch lockout
On/off switch body
On/off switch button
(A)
(B)
(C)
(D)
(A)
(B)
(C)
(D)
When switch lockout (A) isn't pushed down, switch
isn't turned on even if switch trigger (D) is squeezed.
Because heels (C) of the switch lockout (A) obstruct
that the switch trigger (D) pushes switch button (B).
When switch lockout (A) is pushed down, heels (C)
of the switch lockout (A) release switch button (B).
And switch trigger (D) is squeezed, switch button (B)
is pushed by switch trigger (D), and switch is turned
on.
Then motor will turn and blade will immediately start
moving at full speed.