Here's how detached units work.

> When the unit is activated, it gets two actions. Or, rather, the
leader gets 
two
> actions. This is the key to the game. Squads never get actions. Squad
leaders
> get the actions. They can make their guys move (and move with them) or
fire, 
or
> they can do things on their own.

> The leader has two actions. He can use those two actions to make the
guys in 
the
> part of the squad that didn't detach do stuff. This could be move,
fire, what
> have you.

> If he wants the guys in the detached part of the squad to do stuff, he
has to
> transfer an action to those guys. This requires a communication roll.
The
> detached elements of the squad now get two actions.

In the Rules / Activation Chapter :

"If a part of the squad has been divided off as DETACHED ELEMENT for any
reason 
then
one action affects only one of the separated parts of the unit."

Does it mean you can carry out one action with a detached element
whithout 
transferring an action ?