diff --git a/app.go b/app.go
index 9a51c74..036413f 100644
--- a/app.go
+++ b/app.go
@@ -23,7 +23,7 @@ func (a *App) startup(ctx context.Context) {
 		a.station.Fail("could not open the audio device")
 		return
 	}
-	go func() { _ = a.station.Run(runCtx) }()
+	go func() { _ = a.station.Run(runCtx) }() // Run returns when the window closes.
 }
 
 func (a *App) shutdown(context.Context) {
diff --git a/build/darwin/Info.plist b/build/darwin/Info.plist
index d17a747..b742140 100644
--- a/build/darwin/Info.plist
+++ b/build/darwin/Info.plist
@@ -23,6 +23,8 @@
         <string>true</string>
         <key>NSHumanReadableCopyright</key>
         <string>{{.Info.Copyright}}</string>
+        <key>NSMicrophoneUsageDescription</key>
+        <string>funknetz uses the microphone to answer the talk group.</string>
         {{if .Info.FileAssociations}}
         <key>CFBundleDocumentTypes</key>
         <array>
diff --git a/frontend/dist/app.js b/frontend/dist/app.js
index bf1bc26..daff955 100644
--- a/frontend/dist/app.js
+++ b/frontend/dist/app.js
@@ -84,15 +84,5 @@ window.addEventListener("keyup", function (event) {
   }
 });
 
-window.addEventListener("blur", function () {
-  spaceHeld = false;
-  const app = api();
-  if (!app) {
-    return;
-  }
-  app.ReleaseButton();
-  app.ReleaseSpace();
-});
-
 setInterval(refresh, 100);
 refresh();
diff --git a/internal/opus/opus.go b/internal/opus/opus.go
index cbb33fb..038f1eb 100644
--- a/internal/opus/opus.go
+++ b/internal/opus/opus.go
@@ -26,6 +26,7 @@ import (
 	"unsafe"
 )
 
+// FrameSamples is the 20 ms frame at 16 kHz, which is what the reflector carries.
 const FrameSamples = 320
 
 // Encoder produces one raw Opus packet per 20 ms frame.
diff --git a/main.go b/main.go
index 48a6256..0532571 100644
--- a/main.go
+++ b/main.go
@@ -1,5 +1,6 @@
 //go:build !bindings
 
+// Command funknetz is the headset station window.
 package main
 
 import (
diff --git a/main_bindings.go b/main_bindings.go
index 0720908..bad281d 100644
--- a/main_bindings.go
+++ b/main_bindings.go
@@ -1,5 +1,6 @@
 //go:build bindings
 
+// Command funknetz is the headset station window.
 package main
 
 import (
diff --git a/station/behavior_test.go b/station/behavior_test.go
index ff0ff3b..92c2f06 100644
--- a/station/behavior_test.go
+++ b/station/behavior_test.go
@@ -360,6 +360,32 @@ func TestRemoteAudioAndTalker(t *testing.T) {
 	}
 }
 
+func TestPlaybackPausesWhenTransmitting(t *testing.T) {
+	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
+	enc, err := opus.NewEncoder()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer enc.Close()
+	pkt, err := enc.Encode(make([]int16, opus.FrameSamples))
+	if err != nil {
+		t.Fatal(err)
+	}
+	in.refl.writeUDP(t, 101, 7, 1, appendBytes(nil, pkt))
+	in.refl.writeUDP(t, 101, 7, 2, appendBytes(nil, pkt))
+	if _, err := in.st.WaitPlayback(t.Context(), 2*opus.FrameSamples-1); err != nil {
+		t.Fatal(err)
+	}
+	in.st.HoldButton()
+	in.refl.writeFrame(t, 105, appendStr(appendU32(nil, 20), "DB0XYZ"))
+	if _, err := in.st.Wait(t.Context(), func(s station.State) bool { return s.Transmitting }); err != nil {
+		t.Fatal(err)
+	}
+	if pcm := in.st.TakePlayback(); len(pcm) != 0 {
+		t.Fatalf("playback %d samples, want none while transmitting", len(pcm))
+	}
+}
+
 func TestMicrophoneIsNotPlayed(t *testing.T) {
 	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
 	in.st.HoldButton()
diff --git a/station/session.go b/station/session.go
index dc8e457..763d2ac 100644
--- a/station/session.go
+++ b/station/session.go
@@ -163,12 +163,12 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 		case <-ctx.Done():
 			timer.Stop()
 			return ctx.Err()
-		case <-tcpErr:
+		case err := <-tcpErr:
 			timer.Stop()
-			return errors.New("tcp closed")
-		case <-udpFail:
+			return err
+		case err := <-udpFail:
 			timer.Stop()
-			return errors.New("udp closed")
+			return err
 		case tcpf = <-tcpCh:
 			timer.Stop()
 			reason = "tcp"
@@ -465,12 +465,14 @@ func (s *Station) endTransmit() {
 		copy(frame, s.mic)
 		s.mic = nil
 		if pkt, err := s.enc.Encode(frame); err == nil {
+			// A lost datagram ends the session when the receive timer expires.
 			_ = s.sendUDP(udpAudio, appendBlob(nil, pkt))
 		}
 	} else {
 		s.mic = nil
 	}
 	if s.udp != nil {
+		// A lost datagram ends the session when the receive timer expires.
 		_ = s.sendUDP(udpFlush, nil)
 	}
 }
@@ -511,6 +513,7 @@ func (s *Station) publish() {
 		s.state.Transmitting = tx
 		if tx {
 			s.state.Talker = s.cfg.callsign
+			s.play = nil
 		} else {
 			s.state.Talker = s.remoteTalker
 		}
diff --git a/station/station.go b/station/station.go
index 64f2bcf..c9db2b5 100644
--- a/station/station.go
+++ b/station/station.go
@@ -151,6 +151,7 @@ func (s *Station) WriteMicrophone(pcm []int16) {
 		if err != nil {
 			continue
 		}
+		// A lost datagram ends the session when the receive timer expires.
 		_ = s.sendUDP(udpAudio, appendBlob(nil, pkt))
 	}
 }
@@ -159,6 +160,10 @@ func (s *Station) WriteMicrophone(pcm []int16) {
 func (s *Station) TakePlayback() []int16 {
 	s.mu.Lock()
 	defer s.mu.Unlock()
+	if s.transmitting() {
+		s.play = nil
+		return nil
+	}
 	out := s.play
 	s.play = nil
 	return out