barrier composed by plug-in cylindrical heads with a control box with one relay
-S: single beam
-D: double beam
-L: with 10 m cable
barrier composed by plug-in cylindrical heads with a control box with two relays
-S: single beam
-D: double beam
-L: with 10 m cable
barrier composed by plug-in cylindrical heads with a monitored control box with transistor output
-S: single beam
-D: double beam
-L: with 10 m cable