diff --git a/scripts/trassa.gd b/scripts/trassa.gd
index faee683..b203716 100644
--- a/scripts/trassa.gd
+++ b/scripts/trassa.gd
@@ -1,13 +1,21 @@
 class_name trassa_unit extends Node
 
+const ONLINE_TIMEOUT: = 5000
 
 class Trassa extends unit.Unit:
     var source_addr: = []
     func process(tick: int):
+        if (tick - rx_tick) > ONLINE_TIMEOUT:
+            if online:
+                online = false
+                emit_signal('line_changed', self)
         return Error.ERR_BUSY
 
     func _init(unit_name: StringName):
         self.name = unit_name
 
-    func parse(data: PackedByteArray, now_tick: int):
-        pass
+    func parse(data: PackedByteArray, tick: int):
+        rx_tick = tick
+        if not online:
+            online = true
+            emit_signal('line_changed', self)