Surveillance networks are used to observe large areas, like public places, streets, public buildings or private houses, privates premises etc. The surveillance networks often comprise a plurality of surveillance cameras. Such surveillance cameras should be small, robust, trouble-free and have low-maintenance requirements. Subject-matter of the invention is a linear actuator (8) for a linear motion of a component of a camera (1), the linear actuator comprising a supporting structure (6), a motor (10) arranged on the supporting structure for generating a rotational movement, a component carrier (7) for carrying the component and for performing the linear motion relative to the supporting structure, a gear mechanism (11) for transmitting the rotational movement, whereby the last gear of the gear mechanism before the component carrier is a transfer gear (20), whereby the transfer gear comprises a guide way (23a, b, c) extending in rotational direction of the transfer gear with a slope along the guide way whereby the component carrier is coupled with the guide way by resting means (24a, b, c), so that the component carrier is displaced in the linear direction (9) by a rotational movement of the transfer gear due to the slope of the guide way.