diff --git a/V203/usb/scope/software/displaywidget.cpp b/V203/usb/scope/software/displaywidget.cpp
index 37bb0ad..3462e84 100644
--- a/V203/usb/scope/software/displaywidget.cpp
+++ b/V203/usb/scope/software/displaywidget.cpp
@@ -20,6 +20,7 @@ static const double ChannelsSteps [] = {
 };
 static constexpr double   REF_Y  = 3.3;                 // maximum napětí převodníku
 static constexpr double   MAX_Y  = double (1 << 12);    // 12. bit rozlišení - 4096 steps
+static constexpr double   HALF_Y = 0.5 * MAX_Y;
 static constexpr double   STEP_Y = REF_Y / MAX_Y;       // jeden krok ve Voltech
 static constexpr unsigned T_SIZE = 1u << 10;
 static constexpr unsigned T_MASK = T_SIZE - 1u;
@@ -29,13 +30,14 @@ DisplayWidget::DisplayWidget(QWidget * p) : QWidget(p), pcol(), ACopy(), BCopy()
     x_lenght = T_SIZE;
     m_time.a = 200.0;
     m_time.b = 300.0;
-    m_volt.a = 1.0 / STEP_Y;
-    m_volt.b = 2.0 / STEP_Y;
+    m_volt.a = -1.0 / STEP_Y;
+    m_volt.b = +1.0 / STEP_Y;
     m_channels.a = ChannelsSteps[3];
     m_channels.b = ChannelsSteps[3];
-    m_offset.a   = 0.0;
-    m_offset.b   = 0.0;
+    m_offset.a   = 0;
+    m_offset.b   = 0;
     marker_type  = MARKER_TIME;
+    m_TrgSource  = 0;
     int n = 0;
     for (QPointF & e : ChA) { const QPointF p (n++, 0); e = p; }
     n = 0;
@@ -43,6 +45,12 @@ DisplayWidget::DisplayWidget(QWidget * p) : QWidget(p), pcol(), ACopy(), BCopy()
 }
 DisplayWidget::~DisplayWidget() {
 }
+void DisplayWidget::SendTrigerChan(int n) {
+  m_TrgSource = n;
+  drawBackground();
+  update();
+}
+
 void DisplayWidget::MarkerChanged (int n, bool b) {
   if (!b) return;
   // qDebug ("Marker : %d -> %s", n, b ? "true" : "false"); // OK
@@ -90,6 +98,10 @@ void DisplayWidget::wheelEvent(QWheelEvent * event) {
         m_inverse  = m_forward.inverted();
       }
     } break;
+    case OFSET_A: {
+    } break;
+    case OFSET_B: {
+    } break;
     default : {
       qDebug ("wheelEvent : %d", int (m_items));
     } break;
@@ -101,10 +113,12 @@ void DisplayWidget::wheelEvent(QWheelEvent * event) {
 void DisplayWidget::mousePressEvent(QMouseEvent * event) {
   if (m_ts == nullptr) return;
   const QPointF dp = m_inverse.map (event->pos ());
-  // qDebug ("dp:[%g, %g]", dp.x(), dp.y());
+  const double ofs = m_TrgSource ? m_offset.b : m_offset.a;
+  // qDebug ("dp:[%g, %g] %g", dp.x(), dp.y(), ofs);
   switch (m_items) {
     case MOVE_VALUE: {
-      m_ts->value  = dp.y();
+      m_ts->value  = dp.y() - ofs + HALF_Y;
+      // qDebug("Set Triger : %d", m_ts->value);
       emit SettingsChanged (m_items);
     } break;
     case MOVE_OFSET: {
@@ -119,6 +133,12 @@ void DisplayWidget::mousePressEvent(QMouseEvent * event) {
       if (marker_type == MARKER_TIME) m_time.b = dp.x();
       else                            m_volt.b = dp.y();
     } break;
+    case OFSET_A: {
+      m_offset.a = dp.y();
+    } break;
+    case OFSET_B: {
+      m_offset.b = dp.y();
+    } break;
     case TIME_ZOOM: QWidget::mousePressEvent(event); return;
     default : {
       qDebug ("mousePressEvent : %d", int (m_items));
@@ -143,9 +163,13 @@ void DisplayWidget::paintEvent(QPaintEvent * event) {
   QPen pa (pcol.colA, 2);
   QPen pb (pcol.colB, 2);
   p.setPen(pb);
-  p.drawPolyline (m_forward.map(ChB));
+  QMatrix mb (m_forward);
+  mb.translate(0, m_offset.b - HALF_Y);
+  p.drawPolyline (mb.map(ChB));
   p.setPen(pa);
-  p.drawPolyline (m_forward.map(ChA));
+  QMatrix ma (m_forward);
+  ma.translate(0, m_offset.a - HALF_Y);
+  p.drawPolyline (ma.map(ChA));
 }
 void DisplayWidget::setTrigger(TrigerSettings * ts) {
   m_ts = ts;
@@ -189,7 +213,7 @@ void DisplayWidget::reloadMatrix(const QSize & sz) {
   const double ym = sz.height();
   const double xz = xm / (x_lenght);   // převod zpět ma pixely
   const double yz = ym / (MAX_Y);
-  const QMatrix tm (xz,0,0,-yz, 0, ym);
+  const QMatrix tm (xz,0,0,-yz, 0, 0.5 * ym);
   m_forward = tm;
   m_inverse = m_forward.inverted();
 }
@@ -213,36 +237,43 @@ void DisplayWidget::drawBackground() {
   QRect r = background.rect();
   p.fillRect (r, QBrush(Qt::black, Qt::SolidPattern));
   if (!m_ts) return;
-  const double yb = 0.0, ye = MAX_Y;
+  const double yb = 0.0, ye = HALF_Y;
   const double xb = 0.0, xe = x_lenght;
   // rastr
   QPen pg (QColor(64,64,64), 1);
   p.setPen(pg);
   const double dx = 100.0;
   for (double x=xb; x<xe; x+=dx) {
-    const QLineF yline (x, yb, x, ye);
+    const QLineF yline (x, -ye, x, +ye);
     p.drawLine (m_forward.map(yline));
   }
   const double dv = 0.5;
   const double dy = dv / STEP_Y;
   for (double y=yb; y<ye; y+=dy) {
-    const QLineF xline (xb, y, xe, y);
-    p.drawLine (m_forward.map(xline));
+    const QLineF xlinep (xb, +y, xe, +y);
+    p.drawLine (m_forward.map(xlinep));
+    const QLineF xlinem (xb, -y, xe, -y);
+    p.drawLine (m_forward.map(xlinem));
   }
+  QPen pg0 (QColor(128,128,128), 2);
+  p.setPen(pg0);
+  const QLineF hline0 (xb, 0,  xe, 0);
+  p.drawLine (m_forward.map(hline0));
   // triger
-  QPointF trg (m_ts->offset, m_ts->value);
+  const double ofs = (m_TrgSource ? m_offset.b : m_offset.a) - HALF_Y;
+  QPointF trg (m_ts->offset, m_ts->value + ofs);
   QPen pc (QColor(0,0,255), 1);
   p.setPen(pc);
-  const QLineF hline (xb, trg.y(), xe, trg.y());
-  const QLineF vline (trg.x(), yb, trg.x(), ye);
+  const QLineF hline (xb, trg.y(),  xe, trg.y());
+  const QLineF vline (trg.x(), -ye, trg.x(), ye);
   p.drawLine (m_forward.map(hline));
   p.drawLine (m_forward.map(vline));
   // markers
   QPen pm (QColor(255,255,0,196), 2);
   p.setPen(pm);
   if (marker_type == MARKER_TIME) {
-    const QLineF ma (m_time.a, yb, m_time.a, ye);
-    const QLineF mb (m_time.b, yb, m_time.b, ye);
+    const QLineF ma (m_time.a, -ye, m_time.a, ye);
+    const QLineF mb (m_time.b, -ye, m_time.b, ye);
     p.drawLine (m_forward.map(ma));
     p.drawLine (m_forward.map(mb));
   } else {
@@ -251,6 +282,18 @@ void DisplayWidget::drawBackground() {
     p.drawLine (m_forward.map(ma));
     p.drawLine (m_forward.map(mb));
   }
+  // offsets
+  QPen ofpen(pcol.colA);
+  QVector<qreal>dashes;
+  dashes << 5 << 5 << 1 << 5;
+  ofpen.setDashPattern(dashes);
+  p.setPen (ofpen);
+  const QLineF oa (xb, m_offset.a, xe, m_offset.a);
+  p.drawLine (m_forward.map(oa));
+  ofpen.setColor(pcol.colB);
+  p.setPen (ofpen);
+  const QLineF ob (xb, m_offset.b, xe, m_offset.b);
+  p.drawLine (m_forward.map(ob));
   // text
   p.setPen (QPen (pcol.colT));
   QFont font = p.font();
@@ -268,13 +311,14 @@ void DisplayWidget::drawBackground() {
     desc.sprintf("Marker A: %ss, Marker B: %ss, Δ=%ss, f=%sHz", ing_fmt(xz * m_time.a).c_str(), ing_fmt(xz * m_time.b).c_str(),
                                                                 ing_fmt(delta).c_str(), ing_fmt(freq).c_str());
   } else {
-    double scl = 0.0;
+    const double ofs = 0;// HALF_Y + (marker_type == MARKER_VOLT_A ? m_offset.a : m_offset.b);
+    double scl = 0.0; // TODO - ofset to text
     if (marker_type == MARKER_VOLT_A) { p.setPen (QPen (pcol.colA)); scl = m_channels.a; }
     else                              { p.setPen (QPen (pcol.colB)); scl = m_channels.b; }
-    // qDebug("scl = %g", scl);
+    //qDebug("scl = %g, a=%g, b=%g, oa=%g, ob=%g", scl, m_volt.a, m_volt.b, m_offset.a, m_offset.b);
     const double yz = STEP_Y * scl;
-    const double delta = yz * (m_volt.b - m_volt.a);
-    desc.sprintf("Marker A: %sV, Marker B: %sV, Δ=%sV",         ing_fmt(yz * m_volt.a).c_str(), ing_fmt(yz * m_volt.b).c_str(),
+    const double delta = yz * (m_volt.b - m_volt.a), va = m_volt.a + ofs, vb = m_volt.b + ofs;
+    desc.sprintf("Marker A: %sV, Marker B: %sV, Δ=%sV",         ing_fmt(yz * va).c_str(), ing_fmt(yz * vb).c_str(),
                                                                 ing_fmt(delta).c_str());
   }
   p.drawText(10,my, desc);
diff --git a/V203/usb/scope/software/displaywidget.h b/V203/usb/scope/software/displaywidget.h
index 9b496a9..97177b5 100644
--- a/V203/usb/scope/software/displaywidget.h
+++ b/V203/usb/scope/software/displaywidget.h
@@ -28,6 +28,7 @@ class DisplayWidget : public QWidget {
   MOVE_ITEMS  m_items;
   int         m_timeBase;
   int         m_ChBase;
+  int         m_TrgSource;
   double      x_lenght;
   struct MarkSetting {
     double a,b;
@@ -55,6 +56,7 @@ class DisplayWidget : public QWidget {
     void     reloadChRange (int a,  int b);
     void     saveSettings  (QSettings & setting);
     void     restSettings  (QSettings & setting);
+    void     SendTrigerChan(int n);
     
     void resizeEvent    (QResizeEvent * event) override;
     void paintEvent     (QPaintEvent  * event) override;
diff --git a/V203/usb/scope/software/mainwindow.cpp b/V203/usb/scope/software/mainwindow.cpp
index c9cba93..ea52b4e 100644
--- a/V203/usb/scope/software/mainwindow.cpp
+++ b/V203/usb/scope/software/mainwindow.cpp
@@ -89,8 +89,9 @@ void MainWindow::SetSelections(AllSettings as) {
   ui->comboTimeRange->setCurrentIndex(as.part.tim);
   ui->comboVA       ->setCurrentIndex(as.part.asc);
   ui->comboVB       ->setCurrentIndex(as.part.bsc);
-  ui->Display->TimeBaseRange(as.part.tim);
-  ui->Display->reloadChRange(as.part.asc, as.part.bsc);
+  ui->Display->TimeBaseRange (as.part.tim);
+  ui->Display->reloadChRange (as.part.asc, as.part.bsc);
+  ui->Display->SendTrigerChan(as.part.trg.channel);
 }
 
 MainWindow::~MainWindow () {
@@ -133,7 +134,8 @@ void MainWindow::SendTrigerEdge (int n) {
   firmware.SendTrigerEdge(n);
 }
 void MainWindow::SendTrigerChan (int n) {
-  firmware.SendTrigerChan(n);
+  firmware.SendTrigerChan    (n);
+  ui->Display->SendTrigerChan(n);
 }
 void MainWindow::TimeBaseRange (int n) {
   firmware.SendBaseRange(n);