diff --git a/css/signature.css b/css/signature.css
index f8bfb0d..474b476 100644
--- a/css/signature.css
+++ b/css/signature.css
@@ -194,3 +194,31 @@ body {
     font-size: 3em;
     margin-bottom: 20px;
 }
+
+.already-connected-warning {
+    margin-top: 25px;
+    padding: 15px;
+    background: #fff3cd;
+    border: 2px solid #ffc107;
+    border-radius: 8px;
+    display: flex;
+    align-items: flex-start;
+    gap: 12px;
+    text-align: left;
+}
+
+.already-connected-warning .warning-icon {
+    font-size: 1.8em;
+    flex-shrink: 0;
+}
+
+.already-connected-warning .warning-text {
+    flex: 1;
+    color: #856404;
+    font-size: 0.95em;
+    line-height: 1.5;
+}
+
+.already-connected-warning .warning-text strong {
+    font-weight: 600;
+}
diff --git a/html/signature.html b/html/signature.html
index abb3bb8..cf64a2a 100644
--- a/html/signature.html
+++ b/html/signature.html
@@ -24,6 +24,13 @@
                 <div class="icon">📄</div>
                 <h2>Warte auf PDF...</h2>
                 <p>Bereit zum Unterschreiben. Lade ein PDF auf der Master-Station hoch.</p>
+                <div id="alreadyConnectedWarning" class="already-connected-warning" style="display: none;">
+                    <div class="warning-icon">⚠️</div>
+                    <div class="warning-text">
+                        <strong>Hinweis:</strong> Bereits eine andere Signatur-Station ist mit dem Master verbunden.
+                        Diese Station kann nicht verwendet werden, solange die andere Station aktiv ist.
+                    </div>
+                </div>
             </div>
 
             <div id="signatureSection" style="display: none;">
diff --git a/js/signature.js b/js/signature.js
index 3bcf3a9..4d8c4bf 100644
--- a/js/signature.js
+++ b/js/signature.js
@@ -38,7 +38,14 @@ function connectWebSocket() {
     ws.onmessage = async (event) => {
         const data = JSON.parse(event.data);
 
-        if (data.type === 'pdf') {
+        if (data.type === 'already_connected') {
+            console.log('⚠️ Bereits eine andere Signatur-Station verbunden');
+            // Show warning message
+            const warning = document.getElementById('alreadyConnectedWarning');
+            if (warning) {
+                warning.style.display = 'block';
+            }
+        } else if (data.type === 'pdf') {
             console.log('PDF empfangen');
             currentPdf = new Uint8Array(data.pdf);
 
diff --git a/server.js b/server.js
index 1c52a18..f7e61b6 100644
--- a/server.js
+++ b/server.js
@@ -205,6 +205,20 @@ function handleMasterRegister(ws) {
 }
 
 function handleSignatureRegister(ws) {
+    // Check if another signature station is already connected
+    if (signatureConnection && signatureConnection.readyState === WebSocket.OPEN) {
+        // Inform the new station that another station is already connected
+        ws.send(JSON.stringify({
+            type: 'already_connected'
+        }));
+        console.log('⚠️ Neue Signatur-Station versucht sich zu verbinden, aber bereits eine Station verbunden');
+        console.log('⚠️ Neue Station wurde informiert, alte Station bleibt aktiv');
+        // Keep the old connection, don't replace it
+        // Don't register the new connection as signatureConnection
+        return; // Exit without registering the new connection
+    }
+
+    // No existing connection, register this new one
     signatureConnection = ws;
     console.log('Signatur-Station registriert');