initial commit - cross reference with 5th port - obviously has compile errors

code/controllers/subsystem/radio.dm

@@ -0,0 +1,47 @@
+var/datum/subsystem/radio/SSradio
+
+/datum/subsystem/radio
+	name = "Radio"
+	init_order = 18
+	flags = SS_NO_FIRE|SS_NO_INIT
+
+	var/list/datum/radio_frequency/frequencies = list()
+
+/datum/subsystem/radio/New()
+	NEW_SS_GLOBAL(SSradio)
+
+/datum/subsystem/radio/proc/add_object(obj/device, new_frequency as num, filter = null as text|null)
+	var/f_text = num2text(new_frequency)
+	var/datum/radio_frequency/frequency = frequencies[f_text]
+
+	if(!frequency)
+		frequency = new
+		frequency.frequency = new_frequency
+		frequencies[f_text] = frequency
+
+	frequency.add_listener(device, filter)
+	return frequency
+
+/datum/subsystem/radio/proc/remove_object(obj/device, old_frequency)
+	var/f_text = num2text(old_frequency)
+	var/datum/radio_frequency/frequency = frequencies[f_text]
+
+	if(frequency)
+		frequency.remove_listener(device)
+
+		if(frequency.devices.len == 0)
+			qdel(frequency)
+			frequencies -= f_text
+
+	return 1
+
+/datum/subsystem/radio/proc/return_frequency(new_frequency as num)
+	var/f_text = num2text(new_frequency)
+	var/datum/radio_frequency/frequency = frequencies[f_text]
+
+	if(!frequency)
+		frequency = new
+		frequency.frequency = new_frequency
+		frequencies[f_text] = frequency
+
+	return frequency