diff --git a/Machines/Atari2600.cpp b/Machines/Atari2600.cpp
index 787e7fa83..07fab5f7a 100644
--- a/Machines/Atari2600.cpp
+++ b/Machines/Atari2600.cpp
@@ -18,6 +18,7 @@ Machine::Machine()
 	_timestamp = 0;
 	_horizontalTimer = 0;
 	_pixelPosition = 0;
+	_crt = new Outputs::CRT(228);
 }
 
 void Machine::output_pixels(int count)
diff --git a/Machines/Atari2600.hpp b/Machines/Atari2600.hpp
index 43c42b5cb..c21a61b84 100644
--- a/Machines/Atari2600.hpp
+++ b/Machines/Atari2600.hpp
@@ -10,6 +10,7 @@
 #define Atari2600_cpp
 
 #include "../Processors/6502/CPU6502.hpp"
+#include "../Outputs/CRT.hpp"
 
 namespace Atari2600 {
 
@@ -39,6 +40,8 @@ class Machine: public CPU6502::Processor<Machine> {
 		int _pixelPosition;
 		uint8_t _playFieldPixel;
 		void output_pixels(int count);
+
+		Outputs::CRT *_crt;
 };
 
 }
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 51972f70e..17c6e3c0a 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -15,6 +15,7 @@
 		4B14145E1B5887AA00E04248 /* CPU6502AllRAM.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B1414591B58879D00E04248 /* CPU6502AllRAM.cpp */; };
 		4B1414601B58885000E04248 /* WolfgangLorenzTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B14145F1B58885000E04248 /* WolfgangLorenzTests.swift */; };
 		4B1414621B58888700E04248 /* KlausDormannTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B1414611B58888700E04248 /* KlausDormannTests.swift */; };
+		4B366DFC1B5C165A0026627B /* CRT.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B366DFA1B5C165A0026627B /* CRT.cpp */; };
 		4BB298EE1B587D8400A49093 /* 6502_functional_test.bin in Resources */ = {isa = PBXBuildFile; fileRef = 4BB297E01B587D8300A49093 /* 6502_functional_test.bin */; };
 		4BB298EF1B587D8400A49093 /* AllSuiteA.bin in Resources */ = {isa = PBXBuildFile; fileRef = 4BB297E11B587D8300A49093 /* AllSuiteA.bin */; };
 		4BB298F01B587D8400A49093 /* TestMachine.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4BB297E31B587D8300A49093 /* TestMachine.mm */; };
@@ -321,6 +322,8 @@
 		4B14145A1B58879D00E04248 /* CPU6502AllRAM.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = CPU6502AllRAM.hpp; sourceTree = "<group>"; };
 		4B14145F1B58885000E04248 /* WolfgangLorenzTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = WolfgangLorenzTests.swift; sourceTree = "<group>"; };
 		4B1414611B58888700E04248 /* KlausDormannTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = KlausDormannTests.swift; sourceTree = "<group>"; };
+		4B366DFA1B5C165A0026627B /* CRT.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = CRT.cpp; path = ../../Outputs/CRT.cpp; sourceTree = "<group>"; };
+		4B366DFB1B5C165A0026627B /* CRT.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = CRT.hpp; path = ../../Outputs/CRT.hpp; sourceTree = "<group>"; };
 		4B6D7F921B58822000787C9A /* Atari2600.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Atari2600.cpp; sourceTree = "<group>"; };
 		4B6D7F931B58822000787C9A /* Atari2600.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Atari2600.hpp; sourceTree = "<group>"; };
 		4BB297DF1B587D8200A49093 /* Clock SignalTests-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "Clock SignalTests-Bridging-Header.h"; sourceTree = "<group>"; };
@@ -655,6 +658,15 @@
 			name = "Test Binaries";
 			sourceTree = "<group>";
 		};
+		4B366DFD1B5C165F0026627B /* Outputs */ = {
+			isa = PBXGroup;
+			children = (
+				4B366DFA1B5C165A0026627B /* CRT.cpp */,
+				4B366DFB1B5C165A0026627B /* CRT.hpp */,
+			);
+			name = Outputs;
+			sourceTree = "<group>";
+		};
 		4BB297E41B587D8300A49093 /* Wolfgang Lorenz 6502 test suite */ = {
 			isa = PBXGroup;
 			children = (
@@ -930,6 +942,7 @@
 		4BB73E951B587A5100552FC2 = {
 			isa = PBXGroup;
 			children = (
+				4B366DFD1B5C165F0026627B /* Outputs */,
 				4BB73EDC1B587CA500552FC2 /* Machines */,
 				4BB73EDD1B587CA500552FC2 /* Processors */,
 				4BB73EA01B587A5100552FC2 /* Clock Signal */,
@@ -1415,6 +1428,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				4B1414511B5885DF00E04248 /* Atari2600.cpp in Sources */,
+				4B366DFC1B5C165A0026627B /* CRT.cpp in Sources */,
 				4BB73EA41B587A5100552FC2 /* Atari2600Document.swift in Sources */,
 				4B14144E1B5883E500E04248 /* Atari2600.mm in Sources */,
 				4B14145B1B58879D00E04248 /* CPU6502.cpp in Sources */,
diff --git a/OSBindings/Mac/Clock Signal/Atari2600Document.swift b/OSBindings/Mac/Clock Signal/Atari2600Document.swift
index cc92d4d87..49f981b54 100644
--- a/OSBindings/Mac/Clock Signal/Atari2600Document.swift	
+++ b/OSBindings/Mac/Clock Signal/Atari2600Document.swift	
@@ -50,6 +50,8 @@ class Atari2600Document: NSDocument, CSOpenGLViewDelegate {
 	private var lastCycleCount: Int64?
 	func openGLView(view: CSOpenGLView!, didUpdateToTime time: CVTimeStamp) {
 
+		// TODO: treat time as a delta from old time, work out how many cycles that is plus error
+
 		// this slightly elaborate dance is to avoid overflow
 		let intendedCyclesPerSecond: Int64 = 1194720
 		let videoTimeScale64 = Int64(time.videoTimeScale)
diff --git a/Outputs/CRT.cpp b/Outputs/CRT.cpp
new file mode 100644
index 000000000..763864dc6
--- /dev/null
+++ b/Outputs/CRT.cpp
@@ -0,0 +1,27 @@
+//
+//  CRT.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 19/07/2015.
+//  Copyright © 2015 Thomas Harte. All rights reserved.
+//
+
+#include "CRT.hpp"
+
+using namespace Outputs;
+
+CRT::CRT(int cycles_per_line)
+{
+}
+
+void CRT::output_sync(int number_of_cycles)
+{
+}
+
+void CRT::output_level(int number_of_cycles, uint8_t *level, std::string type)
+{
+}
+
+void CRT::output_data(int number_of_cycles, uint8_t *data, std::string type)
+{
+}
diff --git a/Outputs/CRT.hpp b/Outputs/CRT.hpp
new file mode 100644
index 000000000..45be6488b
--- /dev/null
+++ b/Outputs/CRT.hpp
@@ -0,0 +1,28 @@
+//
+//  CRT.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 19/07/2015.
+//  Copyright © 2015 Thomas Harte. All rights reserved.
+//
+
+#ifndef CRT_cpp
+#define CRT_cpp
+
+#include <stdint.h>
+#include <string>
+
+namespace Outputs {
+
+class CRT {
+	public:
+		CRT(int cycles_per_line);
+		void output_sync(int number_of_cycles);
+		void output_level(int number_of_cycles, uint8_t *level, std::string type);
+		void output_data(int number_of_cycles, uint8_t *data, std::string type);
+};
+
+}
+
+
+#endif /* CRT_cpp */