diff --git a/graphics/element.lua b/graphics/element.lua
index edcbdcc..891257d 100644
--- a/graphics/element.lua
+++ b/graphics/element.lua
@@ -3,6 +3,7 @@
 --
 
 local core = require("graphics.core")
+local log  = require("scada-common.log")
 
 local element = {}
 
@@ -46,12 +47,18 @@ local element = {}
 ---|colormap_args
 ---|displaybox_args
 ---|div_args
+---|listbox_args
 ---|multipane_args
 ---|pipenet_args
 ---|rectangle_args
 ---|textbox_args
 ---|tiling_args
 
+---@class element_subscription
+---@field ps psil ps used
+---@field key string data key
+---@field func function callback
+
 -- a base graphics element, should not be created on its own
 ---@nodiscard
 ---@param args graphics_args arguments
@@ -66,6 +73,7 @@ function element.new(args)
         bounds = { x1 = 1, y1 = 1, x2 = 1, y2 = 1 },    ---@class element_bounds
         next_y = 1,
         children = {},
+        subscriptions = {},
         mt = {}
     }
 
@@ -183,6 +191,17 @@ function element.new(args)
 -- luacheck: push ignore
 ---@diagnostic disable: unused-local, unused-vararg
 
+    -- dynamically insert a child element
+    ---@param id string|integer element identifier
+    ---@param elem graphics_element element
+    function protected.insert(id, elem)
+    end
+
+    -- dynamically remove a child element
+    ---@param id string|integer element identifier
+    function protected.remove(id)
+    end
+
     -- handle a mouse event
     ---@param event mouse_interaction mouse interaction event
     function protected.handle_mouse(event)
@@ -281,7 +300,25 @@ function element.new(args)
     ---@nodiscard
     function public.window() return protected.window end
 
-    -- CHILD ELEMENTS --
+    -- delete this element (hide and unsubscribe from PSIL)
+    function public.delete()
+        -- hide + stop animations
+        public.hide()
+
+        -- unsubscribe from PSIL
+        for i = 1, #self.subscriptions do
+            local s = self.subscriptions[i] ---@type element_subscription
+            s.ps.unsubscribe(s.key, s.func)
+        end
+
+        -- delete all children
+        for k, v in pairs(self.children) do
+            v.delete()
+            self.children[k] = nil
+        end
+    end
+
+    -- ELEMENT TREE --
 
     -- add a child element
     ---@nodiscard
@@ -311,12 +348,18 @@ function element.new(args)
 
     -- get a child element
     ---@nodiscard
+    ---@param id element_id
     ---@return graphics_element
-    function public.get_child(key) return self.children[key] end
+    function public.get_child(id) return self.children[id] end
 
-    -- remove child
-    ---@param key string|integer
-    function public.remove(key) self.children[key] = nil end
+    -- remove a child element
+    ---@param id element_id
+    function public.remove(id)
+        if self.children[id] ~= nil then
+            self.children[id].delete()
+            self.children[id] = nil
+        end
+    end
 
     -- attempt to get a child element by ID (does not include this element itself)
     ---@nodiscard
@@ -335,6 +378,25 @@ function element.new(args)
         return nil
     end
 
+    -- DYNAMIC CHILD ELEMENTS --
+
+    -- insert an element as a contained child<br>
+    -- this is intended to be used dynamically, and depends on the target element type.<br>
+    -- not all elements support dynamic children.
+    ---@param id string|integer element identifier
+    ---@param elem graphics_element element
+    function public.insert_element(id, elem)
+        protected.insert(id, elem)
+    end
+
+    -- remove an element from contained children<br>
+    -- this is intended to be used dynamically, and depends on the target element type.<br>
+    -- not all elements support dynamic children.
+    ---@param id string|integer element identifier
+    function public.remove_element(id)
+        protected.remove(id)
+    end
+
     -- AUTO-PLACEMENT --
 
     -- skip a line for automatically placed elements
@@ -460,6 +522,16 @@ function element.new(args)
         protected.response_callback(result)
     end
 
+    -- register a callback with a PSIL, allowing for automatic unregister on delete<br>
+    -- do not use graphics elements directly with PSIL subscribe()
+    ---@param ps psil PSIL to subscribe to
+    ---@param key string key to subscribe to
+    ---@param func function function to link
+    function public.register(ps, key, func)
+        table.insert(self.subscriptions, { ps = ps, key = key, func = func })
+        ps.subscribe(key, func)
+    end
+
     -- VISIBILITY --
 
     -- show the element
diff --git a/rtu/databus.lua b/rtu/databus.lua
index 8ef720e..3014367 100644
--- a/rtu/databus.lua
+++ b/rtu/databus.lua
@@ -7,9 +7,8 @@ local util = require("scada-common.util")
 
 local databus = {}
 
-local dbus_iface = {
-    ps = psil.create()
-}
+-- databus PSIL
+databus.ps = psil.create()
 
 ---@enum RTU_UNIT_HW_STATE
 local RTU_UNIT_HW_STATE = {
@@ -22,54 +21,54 @@ local RTU_UNIT_HW_STATE = {
 databus.RTU_UNIT_HW_STATE = RTU_UNIT_HW_STATE
 
 -- call to toggle heartbeat signal
-function databus.heartbeat() dbus_iface.ps.toggle("heartbeat") end
+function databus.heartbeat() databus.ps.toggle("heartbeat") end
 
 -- transmit firmware versions across the bus
 ---@param rtu_v string RTU version
 ---@param comms_v string comms version
 function databus.tx_versions(rtu_v, comms_v)
-    dbus_iface.ps.publish("version", rtu_v)
-    dbus_iface.ps.publish("comms_version", comms_v)
+    databus.ps.publish("version", rtu_v)
+    databus.ps.publish("comms_version", comms_v)
 end
 
 -- transmit hardware status for modem connection state
 ---@param has_modem boolean
 function databus.tx_hw_modem(has_modem)
-    dbus_iface.ps.publish("has_modem", has_modem)
+    databus.ps.publish("has_modem", has_modem)
 end
 
 -- transmit unit hardware type across the bus
 ---@param uid integer unit ID
 ---@param type RTU_UNIT_TYPE
 function databus.tx_unit_hw_type(uid, type)
-    dbus_iface.ps.publish("unit_type_" .. uid, type)
+    databus.ps.publish("unit_type_" .. uid, type)
 end
 
 -- transmit unit hardware status across the bus
 ---@param uid integer unit ID
 ---@param status RTU_UNIT_HW_STATE
 function databus.tx_unit_hw_status(uid, status)
-    dbus_iface.ps.publish("unit_hw_" .. uid, status)
+    databus.ps.publish("unit_hw_" .. uid, status)
 end
 
 -- transmit thread (routine) statuses
 ---@param thread string thread name
 ---@param ok boolean thread state
 function databus.tx_rt_status(thread, ok)
-    dbus_iface.ps.publish(util.c("routine__", thread), ok)
+    databus.ps.publish(util.c("routine__", thread), ok)
 end
 
 -- transmit supervisor link state across the bus
 ---@param state integer
 function databus.tx_link_state(state)
-    dbus_iface.ps.publish("link_state", state)
+    databus.ps.publish("link_state", state)
 end
 
 -- link a function to receive data from the bus
 ---@param field string field name
 ---@param func function function to link
 function databus.rx_field(field, func)
-    dbus_iface.ps.subscribe(field, func)
+    databus.ps.subscribe(field, func)
 end
 
 return databus
diff --git a/rtu/panel/front_panel.lua b/rtu/panel/front_panel.lua
index 8dcaa1f..4c4aa78 100644
--- a/rtu/panel/front_panel.lua
+++ b/rtu/panel/front_panel.lua
@@ -49,22 +49,22 @@ local function init(panel, units)
     on.update(true)
     system.line_break()
 
-    databus.rx_field("heartbeat", heartbeat.update)
+    heartbeat.register(databus.ps, "heartbeat", heartbeat.update)
 
     local modem = LED{parent=system,label="MODEM",colors=cpair(colors.green,colors.green_off)}
     local network = RGBLED{parent=system,label="NETWORK",colors={colors.green,colors.red,colors.orange,colors.yellow,colors.gray}}
     network.update(5)
     system.line_break()
 
-    databus.rx_field("has_modem", modem.update)
-    databus.rx_field("link_state", network.update)
+    modem.register(databus.ps, "has_modem", modem.update)
+    network.register(databus.ps, "link_state", network.update)
 
     local rt_main = LED{parent=system,label="RT MAIN",colors=cpair(colors.green,colors.green_off)}
     local rt_comm = LED{parent=system,label="RT COMMS",colors=cpair(colors.green,colors.green_off)}
     system.line_break()
 
-    databus.rx_field("routine__main", rt_main.update)
-    databus.rx_field("routine__comms", rt_comm.update)
+    rt_main.register(databus.ps, "routine__main", rt_main.update)
+    rt_comm.register(databus.ps, "routine__comms", rt_comm.update)
 
     --
     -- about label
@@ -74,8 +74,8 @@ local function init(panel, units)
     local fw_v    = TextBox{parent=about,x=1,y=1,text="FW: v00.00.00",alignment=TEXT_ALIGN.LEFT,height=1}
     local comms_v = TextBox{parent=about,x=1,y=2,text="NT: v00.00.00",alignment=TEXT_ALIGN.LEFT,height=1}
 
-    databus.rx_field("version", function (version) fw_v.set_value(util.c("FW: ", version)) end)
-    databus.rx_field("comms_version", function (version) comms_v.set_value(util.c("NT: v", version)) end)
+    fw_v.register(databus.ps, "version", function (version) fw_v.set_value(util.c("FW: ", version)) end)
+    comms_v.register(databus.ps, "comms_version", function (version) comms_v.set_value(util.c("NT: v", version)) end)
 
     --
     -- unit status list
@@ -90,7 +90,7 @@ local function init(panel, units)
     for i = 1, list_length do
         TextBox{parent=threads,x=1,y=i,text=util.sprintf("%02d",i),height=1}
         local rt_unit = LED{parent=threads,x=4,y=i,label="RT",colors=cpair(colors.green,colors.green_off)}
-        databus.rx_field("routine__unit_" .. i, rt_unit.update)
+        rt_unit.register(databus.ps, "routine__unit_" .. i, rt_unit.update)
     end
 
     local unit_hw_statuses = Div{parent=panel,height=18,x=25,y=3}
@@ -102,13 +102,13 @@ local function init(panel, units)
         -- hardware status
         local unit_hw = RGBLED{parent=unit_hw_statuses,y=i,label="",colors={colors.red,colors.orange,colors.yellow,colors.green}}
 
-        databus.rx_field("unit_hw_" .. i, unit_hw.update)
+        unit_hw.register(databus.ps, "unit_hw_" .. i, unit_hw.update)
 
         -- unit name identifier (type + index)
         local name = util.c(UNIT_TYPE_LABELS[unit.type + 1], " ", unit.index)
         local name_box = TextBox{parent=unit_hw_statuses,y=i,x=3,text=name,height=1}
 
-        databus.rx_field("unit_type_" .. i, function (t)
+        name_box.register(databus.ps, "unit_type_" .. i, function (t)
             name_box.set_value(util.c(UNIT_TYPE_LABELS[t + 1], " ", unit.index))
         end)
 
diff --git a/rtu/renderer.lua b/rtu/renderer.lua
index 490959c..17949ce 100644
--- a/rtu/renderer.lua
+++ b/rtu/renderer.lua
@@ -45,10 +45,8 @@ function renderer.close_ui()
         -- stop blinking indicators
         flasher.clear()
 
-        -- hide to stop animation callbacks
-        ui.display.hide()
-
-        -- clear root UI elements
+        -- delete element tree
+        ui.display.delete()
         ui.display = nil
 
         -- restore colors
diff --git a/rtu/startup.lua b/rtu/startup.lua
index 0693f9f..a284b4b 100644
--- a/rtu/startup.lua
+++ b/rtu/startup.lua
@@ -28,7 +28,7 @@ local sna_rtu      = require("rtu.dev.sna_rtu")
 local sps_rtu      = require("rtu.dev.sps_rtu")
 local turbinev_rtu = require("rtu.dev.turbinev_rtu")
 
-local RTU_VERSION = "v1.1.0"
+local RTU_VERSION = "v1.2.0"
 
 local RTU_UNIT_TYPE = types.RTU_UNIT_TYPE
 local RTU_UNIT_HW_STATE = databus.RTU_UNIT_HW_STATE
diff --git a/scada-common/psil.lua b/scada-common/psil.lua
index 664d10d..13dcaa5 100644
--- a/scada-common/psil.lua
+++ b/scada-common/psil.lua
@@ -2,6 +2,8 @@
 -- Publisher-Subscriber Interconnect Layer
 --
 
+local util = require("scada-common.util")
+
 local psil = {}
 
 -- instantiate a new PSI layer
@@ -36,6 +38,15 @@ function psil.create()
         table.insert(self.ic[key].subscribers, { notify = func })
     end
 
+    -- unsubscribe a function from a given key
+    ---@param key string data key
+    ---@param func function function to unsubscribe
+    function public.unsubscribe(key, func)
+        if self.ic[key] ~= nil then
+            util.filter_table(self.ic[key].subscribers, function (s) return s.notify ~= func end)
+        end
+    end
+
     -- publish data to a given key, passing it to all subscribers if it has changed
     ---@param key string data key
     ---@param value any data value
@@ -64,6 +75,9 @@ function psil.create()
         end
     end
 
+    -- clear the contents of the interconnect
+    function public.purge() self.ic = nil end
+
     return public
 end