diff --git a/client.js b/client.js
index b33c6ee..60ef6a6 100644
--- a/client.js
+++ b/client.js
@@ -2,9 +2,7 @@ let calls = {};
 
 let messages = [];
 
-const checkTime = 1000; // 1 second
-const timeOut = 20 * 60 * 1000; // 20 Minutes
-//const timeOut = 60 * 1000; // 1 Minute
+const timeoutLength = 20 * 60 * 1000; // 20 Minutes
 
 Notification.requestPermission(permission => {
   if (permission === "granted") {
@@ -12,32 +10,33 @@ Notification.requestPermission(permission => {
   }
 });
 
-function checkNotHeard() {
-  let now = new Date();
-  for (let call in calls) {
-    let lastHeard = new Date(calls[call]);
-    console.log(call, now - lastHeard);
 
-    if (now - lastHeard > timeOut) {
-      new Notification(`${call} has not been heard for 20 Minutes!`,
-                       {body: `Last Heard: ${lastHeard}`});
-    }
-  };
+function alertNotHeard(callsign) {
+  new Notification(`${callsign} has not been heard for 20 Minutes!`,
+                   {body: `Last Heard: ${calls[callsign].lastHeard.toLocaleTimeString('en-GB')}`});
 }
 
 let aprsStream = new WebSocket("ws://localhost:1234");
 aprsStream.onmessage = function(event) {
   let message = JSON.parse(event.data);
-  let call = `${message.from.call}-${message.from.ssid || 0}`;
-  let date = message.recieved;
+  let callsign = `${message.from.call}-${message.from.ssid || 0}`;
+  let date = new Date(message.recieved);
 
   console.log(message);
-
-  if (call in calls) {
-    message.delta = date - calls[call];
-  }
-  calls[call] = date;
   messages.push(message);
+
+  if (!(callsign in calls)) {
+    calls[callsign] = {
+      lastHeard: date,
+    };
+  }
+
+  else {
+    window.clearTimeout(calls[callsign].timeout);
+  }
+
+  calls[callsign].delta = date - calls[callsign].lastHeard;
+  calls[callsign].timeout = window.setTimeout(
+    alertNotHeard, timeoutLength, callsign);
 };
 
-window.setInterval(checkNotHeard, checkTime);