A sensor which registers mechs and trains attempting to pass by and, if necessary, blocks their movement.

If enabled, detects mechs/trains and blocks their movement if they are coming from any of the directions set by dir. Can currently only be enabled/disabled by radio command and airlocks are updated to utilize this.

The current setup allows mechs to move through airlocks during normal cycles, which for example lets Odysseus out to save lives.
Once a shuttle docks however, the sensors are enabled to prevent boarding.

If blocked, players receive a simple message stating that their command has been overridden.

code/game/machinery/embedded_controller/airlock_program.dm

@@ -16,13 +16,14 @@
 	var/tag_chamber_sensor
 	var/tag_exterior_sensor
 	var/tag_interior_sensor
+	var/tag_mech_sensor
 
 	var/state = STATE_WAIT
 	var/target_state = TARGET_NONE
 
 /datum/computer/file/embedded_program/airlock/New(var/obj/machinery/embedded_controller/M)
 	..(M)
-	
+
 	memory["chamber_sensor_pressure"] = ONE_ATMOSPHERE
 	memory["external_sensor_pressure"] = 0					//assume vacuum for simple airlock controller
 	memory["internal_sensor_pressure"] = ONE_ATMOSPHERE
@@ -32,7 +33,7 @@
 	memory["target_pressure"] = ONE_ATMOSPHERE
 	memory["purge"] = 0
 	memory["secure"] = 0
-	
+
 	if (istype(M, /obj/machinery/embedded_controller/radio/airlock))	//if our controller is an airlock controller than we can auto-init our tags
 		var/obj/machinery/embedded_controller/radio/airlock/controller = M
 		tag_exterior_door = controller.tag_exterior_door? controller.tag_exterior_door : "[id_tag]_outer"
@@ -41,8 +42,9 @@
 		tag_chamber_sensor = controller.tag_chamber_sensor? controller.tag_chamber_sensor : "[id_tag]_sensor"
 		tag_exterior_sensor = controller.tag_exterior_sensor
 		tag_interior_sensor = controller.tag_interior_sensor
+		tag_mech_sensor = controller.tag_mech_sensor? controller.tag_mech_sensor : "[id_tag]_mech"
 		memory["secure"] = controller.tag_secure
-	
+
 		spawn(10)
 			signalDoor(tag_exterior_door, "update")		//signals connected doors to update their status
 			signalDoor(tag_interior_door, "update")
@@ -187,11 +189,11 @@
 			//make sure to return to a sane idle state
 			if(memory["pump_status"] != "off")	//send a signal to stop pumping
 				signalPump(tag_airpump, 0)
-	
+
 	//the airlock will not allow itself to continue to cycle when any of the doors are forced open.
 	if (state && !check_doors_secured())
 		stop_cycling()
-	
+
 	switch(state)
 		if(STATE_PRESSURIZE)
 			if(memory["chamber_sensor_pressure"] >= memory["target_pressure"] * 0.95)
@@ -293,6 +295,11 @@
 			signalDoor(tag_exterior_door, command)
 			signalDoor(tag_interior_door, command)
 
+/datum/computer/file/embedded_program/airlock/proc/enable_mech_regulation()
+	signalDoor(tag_mech_sensor, "enable")
+
+/datum/computer/file/embedded_program/airlock/proc/disable_mech_regulation()
+	signalDoor(tag_mech_sensor, "disable")
 
 /*----------------------------------------------------------
 toggleDoor()