diff --git a/control_seekat_demo.py b/control_seekat_demo.py
index 8f3ad87..7af6cd3 100644
--- a/control_seekat_demo.py
+++ b/control_seekat_demo.py
@@ -31,6 +31,19 @@ class SerComm:
 		self.getobj("dac_resp").set_text(s)
 		return s
 
+	def make_dac_conn(self, f):
+		for x in CHANGE_BUTTONS:
+			self.getobj(x).set_sensitive(False)
+
+		try:
+			f()
+		except Exception as e:
+			self.error_popup(str(e))
+			
+		for x in CHANGE_BUTTONS:
+			self.getobj(x).set_sensitive(True)
+
+	""" make connection (*IDN?) """
 	def connect(self):
 		s = self.sel_box.get_active_id()
 		if self.ser.is_open:
@@ -57,16 +70,23 @@ class SerComm:
 		self.getobj("dac_idn").set_label(self.get_or_to())
 
 	def on_connect(self, _):
-		for x in CHANGE_BUTTONS:
-			self.getobj(x).set_sensitive(False)
+		self.make_dac_conn(self.connect)
 
-		try:
-			self.connect()
-		except Exception as e:
-			self.error_popup(str(e))
-			
-		for x in CHANGE_BUTTONS:
-			self.getobj(x).set_sensitive(True)
+	""" SET """
+	def do_SET(self):
+		if not self.ser.is_open:
+			return None
+		ch = int(self.getobj("SET_ch").get_active_id()) - 1
+		vol = float(self.getobj("SET_v").get_text())
+
+		self.ser.write(bytes(f"SET,{ch},{vol}\r", "UTF-8"))
+		s = self.get_or_to()
+
+		if not s.startswith("DAC"):
+			raise Exception(f"DAC reported an error: {s}")
+
+	def on_SET(self, _):
+		self.make_dac_conn(self.do_SET)
 
 	def refresh(self, _):
 # Does this cause a memory error? This is a GTK interned string
@@ -96,6 +116,7 @@ class SerComm:
 		getobj("sel_ref").connect("clicked", self.refresh)
 		self.refresh(None)
 		getobj("sel_do").connect("clicked", self.on_connect)
+		getobj("SET_do").connect("clicked", self.on_SET)
 
 if __name__ == "__main__":
 	builder = Gtk.Builder()
diff --git a/gui.glade b/gui.glade
index 12a734d..3b1215c 100644
--- a/gui.glade
+++ b/gui.glade
@@ -181,7 +181,7 @@
                     <property name="visible">True</property>
                     <property name="can-focus">True</property>
                     <property name="width-chars">6</property>
-                    <property name="placeholder-text" translatable="yes">10.000</property>
+                    <property name="placeholder-text" translatable="yes">±10</property>
                     <property name="input-purpose">number</property>
                   </object>
                   <packing>
@@ -310,7 +310,7 @@
                         <property name="visible">True</property>
                         <property name="can-focus">True</property>
                         <property name="width-chars">6</property>
-                        <property name="placeholder-text" translatable="yes">start</property>
+                        <property name="placeholder-text" translatable="yes">±10</property>
                         <property name="input-purpose">number</property>
                       </object>
                       <packing>
@@ -336,7 +336,7 @@
                         <property name="visible">True</property>
                         <property name="can-focus">True</property>
                         <property name="width-chars">6</property>
-                        <property name="placeholder-text" translatable="yes">end</property>
+                        <property name="placeholder-text" translatable="yes">±10</property>
                         <property name="input-purpose">number</property>
                       </object>
                       <packing>