IMRaD Journal Vol. 1 Oct. 2017
AUDIO TRANSMISSION VIA VLC Engr. Arlene C. Grate Marc Anthony B. Gonzales Renz Mark C. Rico
----------------------------------------------------------------------------------Abstract- Visible light communications is the emerging technology nowadays. Using visible light to transmit information to the receiver is the basic principle of this technology. Integrating communication to visible light is the main concern of this study. In this paper, the researchers presented a wireless audio transmission using visible light. The system consists of audio source (from microphone or portable devices), transmitter circuit (where the visible light is connected), and a receiver circuit (an audio amplifier with solar cell attached to it).The researchers aim to provide a two-way wireless communication using visible light. Keywords: Visible Light Communication, Wireless Audio Transmission -------------------------------------------------------------------------------------------
Introduction You will not lose your eyesight by looking at the bright side of life (Arlega, Evelyn. 2012). Looking at the bright side of visible light will lead you to the most advanced way of communication, without being hurt of course. Technologies are not made to hurt humankind but to help them live their lives to fullest.
Visible light is only a small portion of the electromagnetic spectrum that fall within the visible range of humans (0.3PHz to 3PHz). Due to the electromagnetic spectrum congestion nowadays, researchers from different parts of the world found a new way of wireless optical communication by utilizing the visible light. Communication using visible light is not harmful to humans because they can perceive it and can act to protect their eyes. It is also not harmful when used in environments that 1
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prohibit the use of wireless communication such as in hospitals, aircrafts, and gasoline stations. Visible light has so many different applications that combine both illumination and communication purposes. Incandescent bulbs, fluorescent lamps, lasers, and especially LEDs are different manmade visible light sources but LEDs are preferred and used to transmit different information signals (data, voice, video, and audio) to the receiver in contrast to the sunlight as the natural visible light source used by Alexander Graham Bell on his photo phone way back 1880’s (Wikipedia). LEDs are now replacing the conventional incandescent bulbs and fluorescent lamps because of its power efficiency, long life, and eco-friendly characteristics. Because of its fast switching capability, it can be used as a communication source by modulating the LED light with the information signal. With LEDs, illumination and communication working at the same time is possible. Other possible applications are just waiting to be discovered. Wireless transmission of information signals conventionally used radio signals and this radio signals cause radiation that is somehow harmful to humans. Another thing with wireless transmission of information signal is that it is prohibited in some environments where there are devices operating at ISM radio bands for it can cause interference to those devices. The researchers want to contribute an alternative way of wireless transmission of signals by utilizing the visible light portion of the spectrum. Transmission of information signals using visible light is not hazardous and will not cause radiation that is why it is a greener, cleaner, and safer way of wireless transmission. Another thing is that it will not cause interference to any devices because this kind of transmission is not using radio waves but light waves. During the course of the study, the following specific objectives are expected to meet: 2
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1. To transmit audio signals using visible light from mobile devices (cellphone, laptop, tablet) to a loudspeaker 2. To transmit human voice signals using visible light from a microphone to a loudspeaker 3. To use the principle of reflection in transmitting audio signals 4. To test the functionality, reliability, efficiency, and effectiveness of this wireless transmission scheme 5. To promote visible light communication, especially to electronics engineering students that will later engage in studies of new technologies.
Methods and Materials
The researchers need the following components and materials in constructing their working prototype. The researchers took into considerations the table of specifications and most specially the prices of the components to have a cost effective system design. Familiarizing with the components will help to know the capabilities and effectiveness of the components when applied to the system. Electret microphone is a type of electrostatic capacitor-based microphone, which eliminates the need for a polarizing power supply by using a permanently charged material. It is a stable dielectric material with a permanently embedded static electric charge. The name electret comes from the words electrostatic and magnet, drawing analogy to the formation of a magnet by alignment of magnetic domains in a piece of iron. Electret microphone, as shown in Figure 40, will be used by the researchers on their prototype if the input to the system is human voice. A DC powered electret microphone operating at 3 volts will be used by the researcher for the transmitter circuit.
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Audio jack plug also known as phone connector or phone jack, is a common family of connector typically used for analog signals, primarily audio. It is cylindrical in shape, typically with two (TS), three (TRS), or four (TRRS) contacts where T stands for tip, R for ring, and S for sleeve. In its original configuration, the outside diameter of the sleeve conductor is 6.35mm. The mini connector has a diameter of 3,5mm and the sub-mini connector has a diameter of 2.5mm. Audio jack plug is often used to connect the output audio terminal of mobile devices to an audio amplifier. A 3.5mm TRS stereo audio jack plug, as shown in Figure 41, will be used by the researchers to connect the audio output terminal of mobile devices to the transmitter circuit. Power LED, as shown in Figure 42, is a two-lead, high power semiconductor light source. Low power LED commonly operates with a 20mA current while high power LED can operate with a wide range of current, ranging from tens of mA to several hundreds of mA. Suitable amount of voltage is needed by the LED so that the electrons will be able to combine with electron holes to release the energy in the form of photons with different particular wavelengths. Different semiconductors used in the manufacture of LEDs will result in different wavelengths (colors) of light emitted. Currently, the brightest semiconductor materials are Aluminum Indium Gallium Phosphide (AlInGaP) for reds, oranges, ambers, and yellows, and Indium Gallium Nitride (InGaN) for blues and greens. A white LED is typically a blue LED coated in a yellow emitting phosphor, or combination of phosphors which are excited by the blue light which is the reason why LEDs appear yellow when they are in the off state. The source of light chosen by the researchers to be used on the prototype is the 1 watt power LED because of limited output voltage and current on the transmitter. 1 watt power LED has a voltage range of 3.2 to 3.6 volts and typical current rating of 300mA and has a luminous intensity of 80 to 90 lumens. It is the chosen because of its inexpensiveness and portability. Its small 4
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size and yet very bright light characteristics make it stand among other light sources. Operational amplifier is a DC-coupled high gain electronic voltage amplifier with a differential input and usually has a single ended output. In this configuration, an operational amplifier produces an output potential that is typically hundreds of thousands of times larger than the potential difference between its input terminals. Due to negative feedback, the characteristics of an operational amplifier circuit, its gain, input and output impedance, bandwidth etc. are determined by external components and have little dependence on temperature coefficients or manufacturing variations in the operational amplifier itself. Operational amplifiers are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. The researchers will use the LM2904D operational amplifier for the transmitter circuit. LM2904D is a low power general purpose dual operational amplifier. It consists of two independent high-gain frequencycompensated operational amplifiers designed to operate from a single supply or dual supply over a wide range of voltages. The terminals of LM2904D, as shown in Figure 43, include (1) output A, (2) inverting input A, (3) non-inverting input A, (4) ground, (5) non-inverting input B, (6) inverting input B, (7) output B, and (8) Vcc. operational. It can be seen that the data sheet came from Texas Instruments but the researchers did not buy their operational amplifier from them but from other manufacturer. Transistors are three-terminal semiconductor devices used to amplify or switch electronic signals and electrical power. The three terminals of transistor as stated earlier are the emitter, base, and collector. A voltage or current applied to one pair of the transistor’s terminals changes the current through another pair of terminals. NPN and PNP are the two types of bipolar junction transistors used for different applications. NPN and PNP are current-controlled transistors that allow current amplification. 5
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The input current on the base of the transistor will be amplified and become larger across the emitter and collector terminals. The internal construction of the two types of bipolar junction transistors is very different with each other meaning, there must be a correct allocation of current and voltage in order for these two devices to work. The researchers will use two NPN transistors; BC547 for electret microphone preamplifier and BC548 for the transmitter circuit. BC547 transistors are essentially the same as the BC548 transistors but selected with higher breakdown voltages. BC548 is low cost and is available in most European Union and many other countries. It is often the first type of bipolar transistor hobbyists’ encounter, and is often featured in designs in hobby electronics magazines where general purpose transistor is required. The letters on the transistors indicates its gain. Letter A indicates low gain (110 to 220 at 2mA), B indicates medium gain (200 to 450), and C indicates high gain (420 to 800). Table 3 is the specifications of the transistors used by the researchers. Capacitors, as shown in Figure 45, originally known as condensers are passive two-terminal electrical components used to store electrical energy temporarily in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors or plates separated by a dielectric. The conductors can be thin films, foils or sintered beads of metal or conductive electrolyte. The non-conducting dielectric acts to increase the capacitor’s charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, air, vacuum, paper, mica, and oxide layers. An ideal capacitor does not dissipate energy but stores energy in the form of an electrostatic field between its plates. Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. Capacitors are often used as filters on most circuits. For low power circuits, common values of capacitors used are in micro Farads. Ceramic Capacitors do not have polarity 6
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while electrolytic capacitors have polarity that is why when working with electrolytic capacitors, be sure to look at its positive and negative terminals before connecting it to the circuit. The researchers will use electrolytic capacitors and some ceramic capacitors on their prototype. Resistors, as shown in Figure 46, are passive two-terminal devices used to limit the flow of current and at the same time used to lower voltage levels in a circuit. Circuits usually used resistors to complement active components such as integrated circuits, operational amplifiers, and microcontrollers. Resistors have different sizes and values and these should be considered in designing because the sizes and values depend upon the application it is to be used. Aside from using generic resistors, the researchers will also use variable resistor or potentiometer, as shown also in Figure 46, for varying the resistance on one part of the circuit. Potentiometers are three terminal resistors with a rotating contact that forms an adjustable voltage divider. It acts as variable resistor or rheostat if only two terminals are used, one end and the rotating contact. Potentiometer is often used as a volume controller. AC adapter or AC to DC converter, as shown in Figure 47, is a type of external power supply, often enclosed in a case similar to an AC plug. Adapters for battery powered devices may be described as chargers or rechargers. Portability is the main concern when it comes to choosing what type of power supply should be used for a certain device. If the device will be installed only on a certain room, a battery is not a good choice but rechargeable battery or AC adapter must be considered. The power supply that the researchers will use on their prototype is a 9-Volt battery or a 9- Volt AC adapter. Solar Cell or photovoltaic cell is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is physical and chemical phenomenon. It is a form of photoelectric cell, defined as a device whose 7
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electrical characteristics, such as current, voltage, or resistance, vary when exposed to light. Solar cells are the building block of photovoltaic modules or solar panels. Solar cells, as shown in Figure 48, are described as being photovoltaic irrespective of whether the source is sunlight or an artificial light. They are used as a photo-detector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity. Multimedia speakers or computer speakers, as shown in Figure 49, are electroacoustic transducers that convert electrical audio signals into corresponding sounds. Most such speakers have an internal amplifier, and consequently require a power source, which may be by a mains power supply often via an AC adapter, batteries, or USB port (able to supply no more than 2.5Watts DC, 500mA at 5Volts). The signal input connector is often a 3.5mm jack plug but RCA connectors are sometimes used. The researchers will be using a USB powered computer speakers with 3.5mm audio jack for their prototype. Printed Circuit Board (PCB), as shown in Figure 50, mechanically supports and electrically connects electronic components using conductive tracks, pads, and other features etched from copper sheets laminated onto a non-conductive substrate. It can be a single sided (one copper layer) double sided (two copper layer), or multi-layer (outer and inner layers). The researchers will be using a pre synthesized printed circuit board for their prototype so that the circuit design is tidy. Breadboard and Jumper Wires Breadboard, as shown in Figure 51, will also be used by the researchers. It will be used for temporary mounting and testing of the prototype. Using breadboard is the easiest way of accomplishing the circuit design with the help of jumper wires. Integrated circuits are often placed in the middle of the breadboard so that the half of the legs is on one side and the half on the other side for easier connections. 8
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After designing the whole circuit for the transmitter and receiver circuits, the researchers will design a casing that will keep all the circuits to make the prototype more presentable. The researchers want to place their receiver circuit on a bamboo or on a closed box. The researchers cannot decide where to put their transmitter circuit because they want to implement it as table lamp but they also want to place it inside a bulb. The researchers plan the dates that they should work to accomplish the requirements and to meet the deadlines. Table 5 shows the planned dates of the researchers in accomplishing their study.
Results and Discussion In line with the visible light communication technology, the proponents’ proposed project about audio transmission via VLC seeks to be comparable to other existing systems. The system uses audio source coming from mobile devices such as laptop, android phones, or tablets and from a microphone with preamplifier circuit. The transmitter circuit uses passive components such as capacitors, resistors, potentiometer and active components such as operational amplifier, transistor, and LED. As the audio source started to pass the very low signal, with 20 to 20 KHz frequency, to the transmitter circuit, the signals started to flow through the 0.1uF ceramic capacitor where direct current components are removed and through the 10kOhm resistor that limits the current to the operational amplifier inverting input pin 6. The 1MOhm potentiometer is a feedback gain controller that controls the signal output from operational amplifier pin 7 passing through the base of the transistor. The transistor worked as a modulator and amplifier in the circuit. The electrolytic capacitors, 470uF and 1000uF, were used as filters to reduce ac components spike in the circuit. Using a voltage divider, the 9 volts supply voltage will be divided into half for powering 9
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the LED. A 9 volt battery or adapter with a maximum of 800mA can be used as a power source for the transmitter circuit. The transistor will modulate and amplify the signal and will pass it to the LED where the signal is being carried by the photons. The arriving signal will be captured by the 6volt, 1.6 watts solar cell where the light will be converted into electrical signal and will be fed to the audio amplifier circuit. To have a two-way wireless communication using visible light, the proponents will provide two transmitters and two receiver circuits. The proponents used LED flashlights as light source which is comparable in luminosity of a 1 watt power LED of about 80 to 100 lumens with beam angle of 30 to 50 degrees and a beam distance of about 7 to 10 meters. LED lights are powered by 4.5 to 6 volts with 200 to 400mA current. The microphone preamplifier is powered by a two AAA 1.5volts battery which added a little voltage to the output LED light when connected as input. When it comes to BC548B transistor, the collector and emitter current are approximately equal to 80mA and the base current is approximately 222uA which gives the total gain of 360 to 400. Based on the BC548B transistor specification the gain of this transistor must be 110 to 450 which is true based on the calculations of the proponents. The collector-emitter voltage is about 4.5 volts which gives a total collector power dissipation of 360mV. All the specifications of the transistor were met by the proponents. The researchers chosen the solar cell as photo detector for their system instead of photodiode or phototransistor because of its wide are coverage, sensitivity, and response time. While solar cell can still deliver output even when the light is slightly focused or dimmed, other photo detectors produce dark currents, currents generated during absence of light, which lessen their sensitivity and response time. Using a solar cell, the output can be delivered on real-time with good quality characteristics.
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When it comes to the modulation of the audio signal, the proponents found out that the modulation used on their system is amplitude modulation. As the volume of the source increases, the amplitude of the sine wave also increases dramatically without affecting the frequency of the signal. On the receiver side, the signal is also amplitude modulated sine wave. In the figure below, the envelope made by amplitude modulation was very evident. For the receiver, the system can use a mono, stereo, or even multiple audio amplifiers as long as the solar cell connected to their inputs must be covered by the LED light source. For the mono audio amplifier, the positive terminal of the solar panel is connected to the tip of the audio jack and the negative terminal connected to the sleeve of the audio jack. For the stereo audio amplifier, there must be two connections for the positive terminal of the solar panel to be connected to the tip and ring of the audio jack and the negative must be connected to the sleeve of the audio jack. For multiple receivers, multiple solar cells are also needed. Connecting in parallel the multiple audio amplifiers to one solar cell is a bad idea because the current produced by the solar cell will be divided on the connected audio amplifiers, thus resulting to a quieter output for all the connected audio amplifiers. The researchers will use stereo speakers for their prototype. Project Limitations and Capabilities A wireless communication system using visible light was successfully developed by the proponents with the purpose of integrating communication to lightings. All systems are not perfect that is why there are limitations and capabilities to be considered. There should be a balancing of the limitations and capabilities of a system before deciding whether the system is advantageous or not. After all the experimentations and testing done by the proponents, the capabilities that they identified on their proposed system are as follows: 11
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1. The system is capable of transmitting high quality audio signals wirelessly coming from mobile devices and microphone using visible light and at the same time can function as illuminator in small area. 2. The transmitter can transmit audio signals at a distance of 5 to 7 meters with acceptable loudness at the receiver side. 3. When the transmitter and receiver are close to each other (at least 1 meter), the transmitted sound is comparable to the sound when the speaker is directly connected to the audio source. 4. The transmitter can also transmit by means of reflection, meaning using a mirror the transmitter can transmit at different angles as long as the light can strike the receiver. 5. The system can be used to any kind of environment especially on hospitals and aircrafts where wireless devices are sometimes prohibited. 6. The system can be deployed by having a single transmitter with multiple receivers. 7. The system is capable of producing consistent output on a real time basis. 8. The system transmission can penetrate transparent blockings on the path of light with a small effect on the received signal. 9. For full-duplex communication, the system is secured as long as the lights are within the area of the communicating party. On the other hand, the system is not that perfect and there are some situations that can be identified as limitations of the system. The limitations that the proponents identified on their system are as follows: 1. Big solid blockings on the path of light can disturb the communication. 2. The system is for short distance (1m to 7m) and point to point optical wireless communication only. 12
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3. The transmitter was not designed for simultaneous transmission of voice and audio signals from mobile devices. 4. Ambient light or other light sources can cause interference to the captured signal by the solar panel, producing unwanted noise on the audio amplifier circuit. Project Evaluation To prove the systems capabilities and limitations stated above are true, the system should undergo the process of evaluation by allowing it to use by the respondents. The respondents will serve as the end user of the system who will express their perception of the system. The system will be evaluated in terms of its functionality, reliability, efficiency, effectiveness, and maintainability. Each criteria have different conditions under and will be rated 1 to 5 where 5 stands for very good, 4 for good, 3 for fair, 2 for poor, and 1 for very poor. The system will be evaluated by four faculty members of Electronics Engineering Department, including the chairperson of ECE, to be able to have an exchange of knowledge with the professionals who have a better understanding of electronics and communications systems. The system will also be evaluated by three faculty members of Computer Engineering Department for them to appreciate where the ECEs are heading in terms of communication and technology. The system will be evaluated with different criteria for functionality, reliability, efficiency and effectiveness, and maintainability. For the functionality criteria, the system will be evaluated if it functions according to the intended purpose, if it can produce the expected outputs in a given period of time, if it is comparable to the existing similar system, if it is easy to use and operate, and if it gives convenience to the users every time they use it. For the reliability criteria, the system will be graded if it can withstand the intended operation, if it is reliable in terms of 13
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strength, capacity, and performance, if high degree of security can be obtained when using the system, if there is consistency on outputs, and if it can satisfy the needed outputs of the user. For the efficiency and effectiveness criteria, the system will be graded if it meets the user’s objectives and requirements, if it can be used to its maximum design capacity, if it can respond to the needs of the end user, if it can contribute for the development of the same model of technology, and if it can enhance the individual’s learning. For the maintainability criteria, the system will be evaluated if it can operate accurately with minimum maintenance, if it can be adapted to any changes in its working condition, and if troubleshooting or repair can be done easily by the user. After grading the system, the respondents should feel free to write comments, suggestions, or recommendations for the improvement of the system. Before the evaluation proper, the respondents should fill up the space provided for their name, complete address, and profession or field of specialization. There is a letter for the respondents asking for their kind evaluation of the system. There is also an instruction that the respondents should follow while evaluating the system. After the evaluation table, there is a space provided for comments, suggestions, or recommendations if they feel that the system needs improvement or modification. After all the chosen respondents finished the evaluation form, it will be collected by the proponents for data analysis. For the interpretation of gathered data, the proponents will use averaging technique on every criterion. In the interpretation of data, the proponents will know if their system is very good, good, fair, poor, or very poor. The results will help the proponents to know if they need improvement of the system or modification on some aspects. This evaluation should reflect the objectives given by the proponents on the first chapter of this paper and the capabilities and limitations of the system as stated earlier. After accomplishing the evaluation instrument by 14
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the responders, the proponents gathered all the data for interpretation. The following data are shown in table 7 with every criterion having the mean value using the averaging technique as stated earlier for computation. For the criteria for functionality, the system was graded very good and good. For the statement the system functions according to the intended purpose was rated good and very good but most of the respondents rated very good that is why the interpretation for this is very good. The proponents agreed to this for they know that they made the system according to its intended purpose based on their objectives stated on the first chapter of this paper. Same with those statements the system can produce the expected outputs in a given period of time, the system is comparable to the existing similar system, the system is easy to use and operate, and the system gives convenience to the users every time they use it, were rated very good. These results are good manifestation that the system performs well when it comes to its functionality. For the proponents, they can say that the idea of the system was not theirs but the system can stand as improvement or modification of other existing systems. For the criteria about reliability, the system was graded very good and good also. The statement the system is reliable in terms of strength, capacity, and performance was interpreted as good. On the other hand, the system was interpreted as very good for the statements the system can withstand the intended operation (continuous or intermittent), the system can satisfy the needed outputs of the user, there is consistency on the outputs, and high degree of security can be obtained when using the system. The proponents can say that their system is reliable enough based on the data that they gathered. Some respondents never realized that the system is also capable of transmitting voice signals that is why there is a security issue on this criterion. The system can be used by two parties as a two-way voice communication which is very secured as long as the lights are within the area of the two 15
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communicating parties in contrast with the RF signals where any interested party can intercept the communication between the two communicating parties. When it comes to the efficiency and effectiveness criteria, the system was graded very good and good. The statements the system meets the user’s objectives and requirements, the system can be used to its maximum design capacity, the system can respond to the needs of the end user, the system can enhance individual’s learning, and the system can contribute for the development of the same model of technology were all interpreted as very good. The statement the system can enhance individual’s learning for the proponents are really true because they can say that they learned a lot while doing their proposed system and they want to share it to everybody who are interested on this kind of technology. Based on the results under this criterion, the system is very efficient and very effective for the users given that the system has its own limitations. Under the maintainability criteria, the system was graded good, very good, and fair. Under this criterion, it is understood that the system troubleshooting or repair can only be done by technicians or any other persons who have knowledge about simple circuitry. The statement the system can operate accurately with minimum maintenance and troubleshooting/repair can be done easily by the user were interpreted as very good because the respondents have a broad knowledge about simple circuits and at the same time the components used by the proponents were minimal that is why the system can be easily repaired. On the other hand, the statement the system can be adapted to any changes on its working condition was interpreted as good. The portability criteria was not included by the proponents on their evaluation instrument but they can say that their system is portable enough to be carried anywhere and can be easily installed because the system was only powered by a 9-volt adapter or 9-volt battery. The system is compatible to any other 16
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devices with audio output such as desktop, laptop, mobile phones, and tablets. System Evaluation Summary Criteria Weighted Average Functionality 4.886 Reliability 4.628 Efficiency and Effectiveness 4.886 Maintainability 4.619 Total Average : 4.755
The system evaluation instrument analysis summary will be used as the basis for the overall performance of the system. Table 8 and Figure 53 show different criteria for system evaluation with corresponding weighted averages. The weighted averages of the criteria were also used again for computation of the total average or can be interpreted as the total performance of the system. It can be seen on the table that the total performance of the system was graded as 4.755 which can be interpreted as very good but the grade clearly say that the system was not perfect or almost perfect. The proponents knew that their proposed system has its own weakness that is why there are space provided for comments, suggestions, and recommendations for them to know what are the things that they should improve and enhance on the system. One of the respondents made a comment that the system was an original concept and the first he had ever seen so far in Columban College. Other respondents left the comments part blank but they discussed to the proponents their comments on the system that can be used for future enhancement of it. The system finally undergone respondents/end users evaluation. The system was graded very good, good, and fair on different criteria such as functionality, reliability, efficiency and effectiveness, and maintainability. These results of the evaluation will be used by the proponents to know the strengths and weaknesses of their system and will be used as basis for 17
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improvement or modification of some aspects of the system. Based on the results of gathered data, the proponents can say that they met their desired output of their proposed system which satisfies their given objectives on the first chapter of this paper. In conclusion, the system being discussed on the whole part of this paper was all about audio transmission by the use of visible light communication. The construction of the system had undergone much experimentation before the proponents arrived to the best design that can output the best and most desirable quality of transmitted signals. The system was evaluated by the respondents who act as end users and their feedbacks on the system were all good. The first objective of the proponents was to transmit audio signals coming from mobile devices using visible light and the proponents can say that this objective was realized because they were able to transmit music wirelessly from mobile phones and laptop using the visible light. Another objective was to transmit human voice signals using visible light and for the proponents they are also able to accomplish this objective for they were able to transmit voice using microphone. The third objective of the proponents was to use the principle of reflection to transmit audio signals and the proponents were able to transmit audio signals using a mirror with small effect on the intensity of light received by the receiver. To test the functionality, reliability, efficiency and effectiveness of the system was also one of the objectives of the researchers and they accomplish this with the help of the evaluation instrument provided to the respondents who evaluated the system. To promote the system to ECE students who will later engage in studies of new technologies was also an objective of the proponents and they successfully accomplished this for some of their respondents came from fourth year ECE students. Based on the results of the gathered data on evaluation instrument, the proponents can therefore
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conclude that they accomplished all the objectives that they cited on the first chapter of this paper.
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Harada, N. et. al. (November 2014). Capturing sound by light: towards massive channel audio sensing via LEDs and video cameras. NTT technical review Vol. 12, No. 11 Haruyama S. (February 2011). Visible light communications: recent activities in Japan. Keio University, Yokohama, Japan Hope, O. et al. (July 2014). Future trends in fiber optics communication. ISBN: 978-988-19252-7-5 Isaac, B. and Song, S. (November 2014). Analysis of Wi-Fi and WiMax and wireless network coexistence. IJCNC Vol. 6, No. 6
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