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_controllers.dm

@@ -7,6 +7,7 @@
 	var/tag_chamber_sensor
 	var/tag_exterior_sensor
 	var/tag_interior_sensor
+	var/tag_mech_sensor
 	var/tag_secure = 0
 
 /obj/machinery/embedded_controller/radio/airlock/initialize()
@@ -43,10 +44,10 @@
 /obj/machinery/embedded_controller/radio/airlock/advanced_airlock_controller/Topic(href, href_list)
 	if(..())
 		return
-	
+
 	usr.set_machine(src)
 	src.add_fingerprint(usr)
-	
+
 	var/clean = 0
 	switch(href_list["command"])	//anti-HTML-hacking checks
 		if("cycle_ext")
@@ -99,10 +100,10 @@
 /obj/machinery/embedded_controller/radio/airlock/airlock_controller/Topic(href, href_list)
 	if(..())
 		return
-	
+
 	usr.set_machine(src)
 	src.add_fingerprint(usr)
-	
+
 	var/clean = 0
 	switch(href_list["command"])	//anti-HTML-hacking checks
 		if("cycle_ext")
@@ -163,10 +164,10 @@
 /obj/machinery/embedded_controller/radio/airlock/access_controller/Topic(href, href_list)
 	if(..())
 		return
-	
+
 	usr.set_machine(src)
 	src.add_fingerprint(usr)
-	
+
 	var/clean = 0
 	switch(href_list["command"])	//anti-HTML-hacking checks
 		if("cycle_ext_door")

code/game/machinery/embedded_controller/airlock_docking_controller.dm

@@ -35,10 +35,10 @@
 /obj/machinery/embedded_controller/radio/airlock/docking_port/Topic(href, href_list)
 	if(..())
 		return
-	
+
 	usr.set_machine(src)
 	src.add_fingerprint(usr)
-	
+
 	var/clean = 0
 	switch(href_list["command"])	//anti-HTML-hacking checks
 		if("cycle_ext")
@@ -77,7 +77,7 @@
 		else
 			enable_override()
 		return
-	
+
 	..(command)
 	airlock_program.receive_user_command(command)	//pass along to subprograms
 
@@ -99,12 +99,14 @@
 
 //we are docked, open the doors or whatever.
 /datum/computer/file/embedded_program/docking/airlock/finish_docking()
+	airlock_program.enable_mech_regulators()
 	airlock_program.open_doors()
 
 //tell the docking port to start getting ready for undocking - e.g. close those doors.
 /datum/computer/file/embedded_program/docking/airlock/prepare_for_undocking()
 	airlock_program.stop_cycling()
 	airlock_program.close_doors()
+	airlock_program.disable_mech_regulators()
 
 //are we ready for undocking?
 /datum/computer/file/embedded_program/docking/airlock/ready_for_undocking()
@@ -115,13 +117,18 @@
 //An airlock controller to be used by the airlock-based docking port controller.
 //Same as a regular airlock controller but allows disabling of the regular airlock functions when docking
 /datum/computer/file/embedded_program/airlock/docking
-	
 	var/datum/computer/file/embedded_program/docking/airlock/master_prog
 
 /datum/computer/file/embedded_program/airlock/docking/receive_user_command(command)
 	if (master_prog.undocked() || master_prog.override_enabled)	//only allow the port to be used as an airlock if nothing is docked here or the override is enabled
 		..(command)
 
+/datum/computer/file/embedded_program/airlock/docking/proc/enable_mech_regulators()
+	enable_mech_regulation()
+
+/datum/computer/file/embedded_program/airlock/docking/proc/disable_mech_regulators()
+	disable_mech_regulation()
+
 /datum/computer/file/embedded_program/airlock/docking/proc/open_doors()
 	toggleDoor(memory["interior_status"], tag_interior_door, memory["secure"], "open")
 	toggleDoor(memory["exterior_status"], tag_exterior_door, memory["secure"], "open")

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()

code/game/machinery/embedded_controller/docking_program_multi.dm

@@ -13,12 +13,12 @@
 
 /datum/computer/file/embedded_program/docking/multi/New(var/obj/machinery/embedded_controller/M)
 	..(M)
-	
+
 	if (istype(M,/obj/machinery/embedded_controller/radio/docking_port_multi))	//if our parent controller is the right type, then we can auto-init stuff at construction
 		var/obj/machinery/embedded_controller/radio/docking_port_multi/controller = M
 		//parse child_tags_txt and create child tags
 		children_tags = text2list(controller.child_tags_txt, ";")
-	
+
 	children_ready = list()
 	children_override = list()
 	for (var/child_tag in children_tags)
@@ -33,13 +33,13 @@
 	var/receive_tag = signal.data["tag"]		//for docking signals, this is the sender id
 	var/command = signal.data["command"]
 	var/recipient = signal.data["recipient"]	//the intended recipient of the docking signal
-	
+
 	if (receive_tag in children_tags)
-		
+
 		//track children status
 		if (signal.data["override_status"])
 			children_override[receive_tag] = signal.data["override_status"]
-	
+
 		if (recipient == id_tag)
 			switch (command)
 				if ("ready_for_docking")
@@ -50,13 +50,13 @@
 					children_override[receive_tag] = 1
 				if ("status_override_disabled")
 					children_override[receive_tag] = 0
-	
+
 	..(signal, receive_method, receive_param)
 
 /datum/computer/file/embedded_program/docking/multi/prepare_for_docking()
 	//clear children ready status
 	clear_children_ready_status()
-	
+
 	//tell children to prepare for docking
 	for (var/child_tag in children_tags)
 		send_docking_command(child_tag, "prepare_for_docking")
@@ -72,14 +72,14 @@
 	//tell children to finish docking
 	for (var/child_tag in children_tags)
 		send_docking_command(child_tag, "finish_docking")
-	
+
 	//clear ready flags
 	clear_children_ready_status()
 
 /datum/computer/file/embedded_program/docking/multi/prepare_for_undocking()
 	//clear children ready status
 	clear_children_ready_status()
-	
+
 	//tell children to prepare for undocking
 	for (var/child_tag in children_tags)
 		send_docking_command(child_tag, "prepare_for_undocking")
@@ -95,7 +95,7 @@
 	//tell children to finish undocking
 	for (var/child_tag in children_tags)
 		send_docking_command(child_tag, "finish_undocking")
-	
+
 	//clear ready flags
 	clear_children_ready_status()
 
@@ -108,7 +108,7 @@
 */
 /datum/computer/file/embedded_program/airlock/multi_docking
 	var/master_tag
-	
+
 	var/master_status = "undocked"
 	var/override_enabled = 0
 	var/docking_enabled = 0
@@ -117,7 +117,7 @@
 
 /datum/computer/file/embedded_program/airlock/multi_docking/New(var/obj/machinery/embedded_controller/M)
 	..(M)
-	
+
 	if (istype(M, /obj/machinery/embedded_controller/radio/airlock/docking_port_multi))	//if our parent controller is the right type, then we can auto-init stuff at construction
 		var/obj/machinery/embedded_controller/radio/airlock/docking_port_multi/controller = M
 		src.master_tag = controller.master_tag
@@ -131,56 +131,58 @@
 			override_enabled = 1
 			broadcast_override_status()
 		return
-	
+
 	if (!docking_enabled|| override_enabled)	//only allow the port to be used as an airlock if nothing is docked here or the override is enabled
 		..(command)
 
 /datum/computer/file/embedded_program/airlock/multi_docking/receive_signal(datum/signal/signal, receive_method, receive_param)
 	..()
-	
+
 	var/receive_tag = signal.data["tag"]		//for docking signals, this is the sender id
 	var/command = signal.data["command"]
 	var/recipient = signal.data["recipient"]	//the intended recipient of the docking signal
-	
+
 	if (receive_tag != master_tag)
 		return	//only respond to master
-	
+
 	//track master's status
 	if (signal.data["dock_status"])
 		master_status = signal.data["dock_status"]
-	
+
 	if (recipient != id_tag)
 		return	//this signal is not for us
-	
+
 	switch (command)
 		if ("prepare_for_docking")
 			docking_enabled = 1
 			docking_mode = 0
 			response_sent = 0
-			
+
 			if (!override_enabled)
 				begin_cycle_in()
-		
+
 		if ("prepare_for_undocking")
 			docking_mode = 1
 			response_sent = 0
-			
+
 			if (!override_enabled)
 				stop_cycling()
 				close_doors()
-		
+				disable_mech_regulation()
+
 		if ("finish_docking")
 			if (!override_enabled)
+				enable_mech_regulation()
 				open_doors()
-		
+
 		if ("finish_undocking")
 			docking_enabled = 0
 
 /datum/computer/file/embedded_program/airlock/multi_docking/process()
 	..()
-	
+
 	if (docking_enabled && !response_sent)
-		
+
 		switch (docking_mode)
 			if (0)	//docking
 				if (ready_for_docking())