area entry guard
area entry guard (to prevent one entering around or behind a protective guard)
man verwendet so etwas im Fall einer Schutzeinrichtung, wenn es ein Lucke gibt, durch die man eintreten könnte, also "Hintertritt"schutz
http://dict.leo.org/forum/viewUnsolvedquery.php?idThread=179...

può esere una griglia ottica, una barriera ottica, ...

Barriere e griglie ottiche SIMATIC FS400
Che si tratti di protezione delle dita o della mano, di protezione di
aree pericolose orizzontali o di protezione d’accesso per aree
estese –
http://docplayer.it/42120489-Sensori-di-sicurezza.html

To reliably detect even the smallest of vio-
lations of the protected zone, the ASIsafe-
enabled FS400 light grids and light cur-
tains operate with a resolution of 50 mm.
A (vertical) light grid safeguards the area
in front of the rotary table against access
from the outside. A (horizontal) light cur-
tain installed lengthwise to the work area
at shin height serves as area entry guard
against intrusions into the danger zone –
http://www.automation.siemens.com/simatic-sensors-static/ftp...