keelan
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rttyjs
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Keelan Lightfoot 8 years ago
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  1. 3
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      README.md
  2. 110
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      rtty.html
  3. 335
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      rtty.js

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README.md View File 

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+# rtty.js
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+
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+A FSK modulator implemented purely in Javascript. Requires a browser with reasonbly good support for Web Audio (Chrome, Safari).

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rtty.html View File 

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+<html>
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+<head>
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+<meta charset="utf-8">
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+<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=yes">
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+<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
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+<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
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+<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
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+<script src="rtty.js"></script>
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+<style>
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+button, input, textarea {
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+	margin-bottom: 10px;
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+}
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+
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+</style>
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+</head>
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+<body>
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+	<div class="container">
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+		<div class="row">
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+			<div class="col-md-12">
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+				<h1>rtty.js</h1>
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+			</div>
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+		</div>
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+
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+		<div class="row">
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+			<div class="col-md-4">
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+				<div class="panel panel-default">
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+					<div class="panel-heading"><h3 class="panel-title">Output Control</h3></div>
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+					<div class="panel-body">
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+						<b>Baud Rate:</b> <input class="form-control" id="baudrate" type="number" value="45.45">
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+						<b>Mark Frequency:</b> <input class="form-control" id="markfrequency" type="number" value="2125">
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+						<b>Space Frequency:</b> <input class="form-control" id="spacefrequency" type="number" value="2295">
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+						<button class="btn btn-default" id="start">Start Audio</button>
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+						<button class="btn btn-default" id="stop">Stop Audio</button>
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+						<button class="btn btn-default" id="invert">Invert</button>
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+					</div>
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+				</div>
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+				<div class="panel panel-default">
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+					<div class="panel-heading"><h3 class="panel-title">Modulator Control</h3></div>
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+					<div class="panel-body">
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+						<button class="btn btn-default" id="pause">Pause</button>
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+						<button class="btn btn-default" id="resume">Resume</button>
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+						<button class="btn btn-default" id="flush">Flush Buffer</button>
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+					</div>
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+				</div>
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+			</div>
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+			<div class="col-md-8">
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+				<div class="panel panel-default">
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+					<div class="panel-heading"><h3 class="panel-title">Input</h3></div>
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+					<div class="panel-body">
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+<textarea class="form-control" id="data" rows="14">
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+Is it a fact—or have I dreamt it—that, by means of electricity, the world of matter has become a great nerve, vibrating thousands of miles in a breathless point of time?
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+</textarea>
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+						<button class="btn btn-default" id="encode">Encode</button>
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+					</div>
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+				</div>
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+			</div>
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+		</div>
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+	</div>
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+</body>
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+<script>
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+
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+	var modulator = new RTTY({
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+		baudrate: parseFloat(document.querySelector('#baudrate').value),
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+		mark: parseFloat(document.querySelector('#markfrequency').value),
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+		space: parseFloat(document.querySelector('#spacefrequency').value)
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+	});
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+
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+	modulator.bufferEmptyCallback = function() {
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+	};
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+
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+	document.querySelector('#start').onclick = function() {
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+		document.querySelector('#baudrate').disabled=true;
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+		document.querySelector('#markfrequency').disabled=true;
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+		document.querySelector('#spacefrequency').disabled=true;
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+		modulator.baudrate = parseFloat(document.querySelector('#baudrate').value);
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+		modulator.mark = parseFloat(document.querySelector('#markfrequency').value);
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+		modulator.space = parseFloat(document.querySelector('#spacefrequency').value);
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+		modulator.startSound();
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+	};
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+
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+	document.querySelector('#stop').onclick = function() {
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+		modulator.stopSound();
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+		document.querySelector('#baudrate').disabled=false;
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+		document.querySelector('#markfrequency').disabled=false;
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+		document.querySelector('#spacefrequency').disabled=false;
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+	};
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+
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+	document.querySelector('#invert').onclick = function() {
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+		modulator.invert();
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+	};
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+
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+	document.querySelector('#pause').onclick = function() {
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+		modulator.pauseModulation();
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+	};
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+
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+	document.querySelector('#resume').onclick = function() {
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+		modulator.resumeModulation();
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+	};
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+
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+	document.querySelector('#encode').onclick = function() {
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+		modulator.modulate(document.querySelector('#data').value);
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+
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+	};
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+
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+	document.querySelector('#flush').onclick = function() {
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+		modulator.flushBuffer();
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+	};
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+
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+</script>
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+</html>

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rtty.js View File 

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+var RTTY = RTTY || {};
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+
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+var RTTY = function(props) {
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+
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+    this.mark = props.mark;
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+	this.space = props.space;
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+	this.baudrate = props.baudrate;
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+
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+	this.bufferEmptyCallback = null;
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+	this.characterDoneCallback = null;
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+
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+	this.fadeDoneCallback = null;
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+
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+    this.audioCtx = new (window.AudioContext || window.webkitAudioContext)();
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+
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+	this.osc = 0;
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+	this.freq = this.mark;
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+
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+	this.buffer = [];
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+	this.bufferOffset = 0;
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+
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+	this.idleBits = 0;
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+
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+	this.bit = 8;
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+	this.ct = {};
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+	this.figsmask = 1<<5;
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+	this.currentchar = 0x00;
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+	this.pause = false;
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+	this.suspend = false;
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+	this.source = null;
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+	this.figures = true;
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+	this.unshift = false;
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+	this.idle = true;
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+	this.bufferEmptyCalled = false;
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+	this.flush = null;
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+	this.amplitude = 1;
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+	this.fade = 0;
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+
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+	this.initTables();
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+
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+	this.scriptNode = this.audioCtx.createScriptProcessor(4096, 1, 1);
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+
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+	this.scriptNode.onaudioprocess = (function(audioProcessingEvent) {
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+		var inputBuffer = audioProcessingEvent.inputBuffer;
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+		var outputBuffer = audioProcessingEvent.outputBuffer;
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+		var inputData = inputBuffer.getChannelData(0);
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+		var outputData = outputBuffer.getChannelData(0);
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+		for (var sample = 0; sample < inputBuffer.length; sample++) {
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+			if (!this.suspend && inputData[sample]==1) { // bit marker
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+				if (this.idleBits > 0) {
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+					this.idleBits--;
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+					if (this.idleBits==0) {
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+						if (this.characterDoneCallback != null && typeof this.characterDoneCallback == "function") {
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+							this.characterDoneCallback(bufferLen);
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+						}
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+						this.idle = true;
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+					}
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+				} else if (this.pause && this.idle) {
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+					this.suspend = true;
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+					this.pause = false;
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+				} else if (this.idle) {
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+					if (this.flush != null) {
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+						this.buffer = [];
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+						this.bufferOffset = 0;
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+						if (typeof this.flush == "function") {
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+							this.flush();
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+						}
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+						this.flush = null;
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+					}
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+					var bufferLen = this.buffer.length - this.bufferOffset;
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+					if (bufferLen > 0)  {
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+						this.idle = false;
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+						if (this.bufferEmptyCalled) {
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+							this.bufferEmptyCalled = false;
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+						}
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+						var next = this.buffer[this.bufferOffset];
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+						if (++this.bufferOffset * 2 >= this.buffer.length){
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+							this.buffer  = this.buffer.slice(this.bufferOffset);
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+							this.bufferOffset = 0;
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+						}
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+						switch (next.type) {
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+						case "char":
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+							this.currentchar = next.val;
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+							break;
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+						case "pause":
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+							this.idleBits = next.val;
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+							break;
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+						case "callback":
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+							next.val();
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+							this.idle = true;
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+							break;
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+						}
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+					} else if (!this.bufferEmptyCalled) {
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+						if (this.bufferEmptyCallback != null && typeof this.bufferEmptyCallback == "function") {
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+							this.bufferEmptyCallback();
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+							this.bufferEmptyCalled = true;
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+						}
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+					}
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+				} else {
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+					if (this.bit==0) { // start
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+						this.freq = this.space;
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+					}
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+					if (this.bit >= 1 && this.bit <= 5) { // data bits
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+						this.freq = (this.currentchar&1)?this.mark:this.space;
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+						this.currentchar=this.currentchar>>1;
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+					}
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+					if (this.bit==6||this.bit==7) { // stop bits
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+						this.freq = this.mark;
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+					}
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+					if (this.bit==8) {
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+						this.bit=0;
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+						this.idle=true;
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+						if (this.characterDoneCallback != null && typeof this.characterDoneCallback == "function") {
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+							this.characterDoneCallback(bufferLen);
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+						}
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+					} else {
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+						this.bit++;
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+					}
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+				}
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+			}
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+
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+			outputData[sample] =  this.waveTable[this.osc]*this.amplitude;
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+			this.osc = (this.osc+this.freq)%this.audioCtx.sampleRate;
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+
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+			if (this.fade > 0 && (this.amplitude + this.fade) > 1) {
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+				this.fade = 0;
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+				this.amplitude = 1;
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+				if (this.fadeDoneCallback != null && typeof this.fadeDoneCallback == "function") {
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+					this.fadeDoneCallback();
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+					this.fadeDoneCallback = null;
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+				}
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+			} else if (this.fade < 0 && (this.amplitude + this.fade) < 0) {
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+				this.fade = 0;
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+				this.amplitude = 0;
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+				if (this.fadeDoneCallback != null && typeof this.fadeDoneCallback == "function") {
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+					this.fadeDoneCallback();
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+					this.fadeDoneCallback = null;
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+				}
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+			}
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+			this.amplitude += this.fade;
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+		}
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+	}).bind(this);
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+
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+}
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+
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+RTTY.prototype.initTables = function() {
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+	this.waveTable = new Float32Array(this.audioCtx.sampleRate);
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+	for (var i=0;i<this.audioCtx.sampleRate;i++) {
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+		this.waveTable[i] = Math.sin((i/this.audioCtx.sampleRate)*2*Math.PI);
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+	}
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+	this.ct = {
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+		"0": 0x36, "1": 0x37, "2": 0x33, "3": 0x21, "4": 0x2a, "5": 0x30, "6": 0x35,
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+		"7": 0x25, "8": 0x26, "9": 0x38, "A": 0x03, "B": 0x19, "C": 0x0e, "D": 0x09,
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+		"E": 0x01, "F": 0x0d, "G": 0x1a, "H": 0x14, "I": 0x06, "J": 0x0b, "K": 0x0f,
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+		"L": 0x12, "M": 0x1c, "N": 0x0c, "O": 0x18, "P": 0x16, "Q": 0x17, "R": 0x0a,
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+		"S": 0x05, "T": 0x10, "U": 0x07, "V": 0x1e, "W": 0x13, "X": 0x1d, "Y": 0x15,
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+		"Z": 0x11, "\r": 0x02, "\n": 0x08, "'": 0x2b, "-": 0x23, "_": 0x23, ",": 0x2c,
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+		"!": 0x2d, ":": 0x2e, "(": 0x2f, "+": 0x31, ")": 0x32, "#": 0x34, "?": 0x39,
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+		"&": 0x3a, ".": 0x3c, "/": 0x3d, ";": 0x3e, "$": 0x29
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+	}
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+};
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+
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+
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+RTTY.prototype.setFade = function(fade, callback) {
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+	this.fade = fade;
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+	this.fadeDoneCallback = callback;
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+}
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+
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+RTTY.prototype.pauseModulation = function() {
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+	this.pause = true;
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+}
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+
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+RTTY.prototype.resumeModulation = function() {
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+	this.suspend = false;
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+}
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+
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+
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+
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+RTTY.prototype.startSound = function() {
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+	if (this.source == null) {
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+		this.idle = true;
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+		this.amplitude = 0;
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+		var samplesPerSymbol = Math.floor(this.audioCtx.sampleRate/this.baudrate);
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+		var myArrayBuffer = this.audioCtx.createBuffer(1, samplesPerSymbol, this.audioCtx.sampleRate);
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+		this.source = this.audioCtx.createBufferSource();
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+		this.source.buffer = myArrayBuffer;
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+		this.source.loop = true;
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+
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+		var tickTrack = myArrayBuffer.getChannelData(0);
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+		tickTrack[0] = 1;
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+
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+		this.freq = this.mark;
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+
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+		this.source.connect(this.scriptNode);
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+		this.scriptNode.connect(this.audioCtx.destination);
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+		this.source.start();
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+
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+		this.setFade(.01, null);
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+	}
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+}
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+
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+RTTY.prototype.stopSound = function() {
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+	if (this.source != null) {
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+		var me = this
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+		this.flushBuffer(function(){
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+			me.setFade(-.01, function(){
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+				setTimeout(function(){
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+					me.source.stop();
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+	 				me.scriptNode.disconnect();
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+	 				me.source = null;
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+				}, 500);
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+			});
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+		});
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+	}
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+}
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+
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+RTTY.prototype.flushBuffer = function(callback) {
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+	if (callback == null) {
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+		callback=function(){};
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+	}
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+	this.flush = callback;
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+}
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+
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+RTTY.prototype.invert = function() {
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+	var x = this.mark;
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+	if (this.freq==this.mark) {
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+		this.freq=this.space;
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+	} else {
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+		this.freq=this.mark;
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+	}
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+	this.mark = this.space;
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+	this.space = x;
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+}
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+
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+
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+RTTY.prototype.modulate = function(str) {
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+	for (var i = 0, len = str.length; i < len; i++) {
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+		this.modulateChar(str[i]);
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+	}
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+}
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+
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+RTTY.prototype.modulateChar = function(c) {
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+	var baudot
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+
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+	var c = c.toUpperCase();
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+
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+	switch (c) {
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+		case 0x00: // null
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+			this.pushChar(0x00); // null
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+			break;
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+		case 0x0a: // lf
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+			this.pushChar(0x02); // cr
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+			this.pushChar(0x08); // lf
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+			break;
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+		case ' ': // space
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+			// if we print a space in figures mode, terminals set to
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+			// unshift on space will unshift. Remember that, so that if a
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+			// figures character needs to be printed, we can turn figures
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+			// mode back on before printing it.
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+			if (this.figures) {
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+				this.unshift = true;
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+			}
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+			this.pushChar(0x04);
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+			break;
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+		case '@': // Change @ to (at)
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+			this.figs();
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+			this.pushChar(this.ct['(']);
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+			this.ltrs();
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+			this.pushChar(this.ct['A']);
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+			this.pushChar(this.ct['T']);
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+			this.figs();
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+			this.pushChar(this.ct[')']);
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+			break;
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+		case '"': // use two single quotes as a double quote
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+			this.figs();
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+			this.pushChar(this.ct["'"]);
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+			this.pushChar(this.ct["'"]);
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+			break;
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+		default:
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+			baudot=this.ct[c];
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+			if (baudot!=undefined) {
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+				// correction for unshift on space
283 
+				if ((baudot&this.figsmask)&&this.figures&&this.unshift) {
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+					this.figs();
285 
+				}
286 
+				if ((baudot&this.figsmask)&&!this.figures) {
287 
+					this.figs();
288 
+				}
289 
+				if (!(baudot&this.figsmask)&&this.figures) {
290 
+					this.ltrs();
291 
+				}
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+				this.pushChar(baudot);
293 
+			}
294 
+			break;
295 
+	}
296 
+
297 
+}
298 
+
299 
+RTTY.prototype.pushChar = function(c) {
300 
+	this.buffer.push({
301 
+		type: "char",
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+		val: c
303 
+	});
304 
+
305 
+}
306 
+
307 
+RTTY.prototype.pushPause = function(p) {
308 
+	this.buffer.push({
309 
+		type: "pause",
310 
+		val: p
311 
+	});
312 
+}
313 
+
314 
+RTTY.prototype.pushCallback = function(callback) {
315 
+	this.buffer.push({
316 
+		type: "callback",
317 
+		val: callback
318 
+	});
319 
+}
320 
+
321 
+
322 
+RTTY.prototype.figs = function() {
323 
+	this.pushChar(0x1b); // figs
324 
+	this.figures=true;
325 
+	this.unshift=false;
326 
+}
327 
+
328 
+RTTY.prototype.ltrs = function() {
329 
+	this.pushChar(0x1f); // ltrs
330 
+	this.figures=false;
331 
+	this.unshift=false;
332 
+}
333 
+
334 
+
335 
+