/datum/radio_frequency
	var/frequency as num
	var/list/list/obj/devices = list()

/datum/radio_frequency/proc/post_signal(obj/source, datum/signal/signal, filter = null, range = null)
	var/turf/start_point
	if(range)
		start_point = get_turf(source)
		if(!start_point)
			qdel(signal)
			return 0
	if (filter)
		send_to_filter(source, signal, filter, start_point, range)
		send_to_filter(source, signal, RADIO_DEFAULT, start_point, range)
	else
		//Broadcast the signal to everyone!
		for (var/next_filter in devices)
			send_to_filter(source, signal, next_filter, start_point, range)

//Sends a signal to all machines belonging to a given filter. Should be called by post_signal()
/datum/radio_frequency/proc/send_to_filter(obj/source, datum/signal/signal, filter, turf/start_point = null, range = null)
	if (range && !start_point)
		return

	for(var/obj/device in devices[filter])
		if(device == source)
			continue
		if(range)
			var/turf/end_point = get_turf(device)
			if(!end_point)
				continue
			if(start_point.z != end_point.z || get_dist(start_point, end_point) > range)
				continue

		device.receive_signal(signal, TRANSMISSION_RADIO, frequency)

/datum/radio_frequency/proc/add_listener(obj/device, filter)
	if (!filter)
		filter = RADIO_DEFAULT
	//log_debug("add_listener(device=[device],filter=[filter]) frequency=[frequency]")
	var/list/obj/devices_line = devices[filter]
	if (!devices_line)
		devices_line = new
		devices[filter] = devices_line
	devices_line+=device
//			var/list/obj/devices_line___ = devices[filter_str]
//			var/l = devices_line___.len
	//log_debug("DEBUG: devices_line.len=[devices_line.len]")
	//log_debug("DEBUG: devices(filter_str).len=[l]")

/datum/radio_frequency/proc/remove_listener(obj/device)
	for (var/devices_filter in devices)
		var/list/devices_line = devices[devices_filter]
		devices_line-=device
		while (null in devices_line)
			devices_line -= null
		if (devices_line.len==0)
			devices -= devices_filter
			del(devices_line)