2009 California Vehicle Code - Section 28080-28081 :: Article 12. Camper Signaling Devices

28080.  (a) Every motor vehicle upon which a camper is mounted shall
be equipped with an audible or visual signaling device which can be
activated from inside the camper and which is constructed so as to
allow any person inside the camper to gain the attention of the
driver of the motor vehicle. In no event shall a horn, as required by
Section 27000, be used to comply with this subdivision.
   (b) No person shall drive a motor vehicle upon which is mounted a
camper containing any passenger unless the motor vehicle is equipped
as required by subdivision (a).

28081.  The provisions of Section 28080 shall not apply to either of
the following:
   (a) Any motor vehicle upon which a camper is mounted if a person
is able to move between the cab portion of the motor vehicle and the
camper.
   (b) Any motor vehicle upon which a camper is mounted, which motor
vehicle is equipped with a sliding or removable rear window which can
be opened or removed by a person inside such camper.