The George Washington University
School of Engineering and Applied Science
Department of Electrical and Computer Engineering
Final Design Review (FDR) Report
Design of a Wireless Stereo Speakers System
By
Alshawwa, Nawaf
Prepared for
EE – 163
Senior Electrical and Computer Engineering
Design Project Laboratory
Prof. Joseph R. Silverman
Sunday, March 06, 2016
©2000 Nawaf Alshawwa All Rights Reserved
Abstract of the Final Design Report
Wireless Speakers System
By
Nawaf Alshawwa
This report is a Final Design Review (FDR) to design, build, and test a Wireless
Speakers System. The Wireless Speakers will be able to play music from any audio
device such as a CD player or TV. The transmitter will transmit audio signals to the
receiver up to a distance of 7 meters. The Wireless Speakers system will operate at Radio
Frequency (RF) signals. Specifically, it will utilize Frequency Modulation (FM)
techniques to transmit the audio signals. The System is designed to transmit and receive
the audio signal on a 48MHz frequency, which is a free band for those that are not
licensed or commercial. The system will be powered using an AC outlet.
In this report all the major aspects of the design will be defined. These definitions
will include description of the design in a top-down approach, specifications, block
diagrams, schematics, Gantt charts, economic analysis, and various testing techniques. It
will also include a comparative product survey as well as a user manual.
The project will require 36 weeks to complete and will expend an estimated 588.5
person hours of labor at an estimated total cost of $13,765. As of November 11th the
actual person hours has decreased to 552 hours at a cost of $13,077. At this point we are
ending the design phase and entering the building and testing phase. Project report # 1
will be on December 2nd. A working prototype will be available by April 27th, 2000. The
estimated total cost of the prototype is $46,418, but the actual cost of the prototype stand
at $44,116 so far. A preliminary economic analysis has determined that 100,000 units
will be sold at a cost to the company of $106 per unit including indirect Administrative
and General costs (A&G). This price also includes a 20 % profit to the company.
Estimated retail price for the Wireless Speakers System is $190.
©2000 Nawaf Alshawwa All Rights Reserved
1
Acknowledgements
It is the author’s pleasure to mention and thank the following persons, without whom this
design would have not been possible to complete:
-
Professor J.R. Silverman, for providing generous amount of criticism, monitoring the
progress of the design, and being the driving force in getting it done;
-
Jimmy Alatishe, for helping me with the background of Frequency Modulation, and in
directing me with the purchasing of parts.
-
Professor Milos Doroslovaki, for his input on some parts of the design and making sure that
the design is going in the right direction.
-
Mohammed Afridi, for his assistance with designing some parts of the project and his
expertise in selecting parts for the design.
-
Hisham Hamed, for his efforts is explaining some theories about Frequency Modulation,
oscillators, and demodulation techniques.
©2000 Nawaf Alshawwa All Rights Reserved
2
Table of Contents
Section
Page
Abstract
1
Acknowledgements
2
Table of Contents
3
List of Tables
4
Table of Figures
5
Introduction
6
Specifications
9
Theory & Description of the Design
11
I. Transmitter
12
II. Receiver (L & R speakers)
26
Physical Layout of the design
35
History of the Project
37
Test of Design
39
Gantt Charts
40
Labor cost vs. Time graph
43
Parts List
44
Economic Analysis
45
Comparative Product Survey
47
Conclusion
48
References
49
Appendix
A. Module / Matrix
50
B. User Manual
52
C. Data Sheets
59
D. Log Book
60
©2000 Nawaf Alshawwa All Rights Reserved
3
List of Tables
Section
Page
Table 1: CA3090 pinouts
32
Table 2: Ten Deliverables Gantt Chart
40
Table 3: CDR to FDR Gantt Chart
41
Table 4: FDR to PR#1 Gantt Chart
42
Table 5: Parts List
44
©2000 Nawaf Alshawwa All Rights Reserved
4
Table of Figures
Section
Page
Figure 1: Layout of Wireless Speakers System Block Diagram
11
Figure 2: Transmitter Block Diagram
12
Figure 3: Low pass filter schematics
13
Figure 4: Output of the low pass filter
13
Figure 5: Pre-Amp Circuit
14
Figure 6: Output simulation of the Pre-Amp
14
Figure 7:Balance control schematics
15
Figure 8: Graphic Equalizer Schematics
17
Figure 9: Graphic Equalizer Spectrum
18
Figure 10: Volume Control Network.
19
Figure 11: FM Stereo Spectrum
20
Figure 12: Mixer Module
21
Figure 13: Sine Wave Oscillator
22
Figure 14: Mixer of left and right channels
23
Figure 15: Voltage Controlled Oscillator
25
Figure 16: Transmitter’s Power Amplifier
26
Figure 17: Receiver Block Diagram
27
Figure 18: RF amplifier (preselector)
28
Figure 19: Receiver Pre-Amp.
29
Figure 20: PLL Block Diagram
29
Figure 21: FM stereo decoder
30
Figure 22: Stereo matrix Decoder
33
Figure 23: Receiver Power amplifier
34
Figure 24: connector Headphone to Y-Adapter
36
Figure 25: Labor cost vs. Time graph
43
©2000 Nawaf Alshawwa All Rights Reserved
5
Introduction
Wireless speakers have been around for a long time. In fact, the first ones were
introduced to the public in the 1940’s. Unfortunately though, they were plagued with
problems of static, interference and low power.
Nowadays, wireless speakers are as clear as any other speaker system that is
corded. This comes as no surprise because of the new technological advances in circuitry
and wireless products. These types of speakers give the user the freedom to listen to
music anywhere he/she favors. In addition, but this new trend of sound systems can also
be used with TVs, Stereo receivers, and CD players…etc among others.
The design of the project analyzed in these documents pertains to music listeners,
especially those who prefer to listen to music in various places without any constraints.
The speakers will pick up the music from across walls and can be arranged in many ways
around the house. The design in hand utilizes frequency modulation techniques for
modulation and demodulation.
Frequency modulation (FM) technique is considered to be one of the hardest
methods to achieve. It is also favored over amplitude modulation because of its lower
sensitivity to noise and interference, as well as its ability to conserve more power in its
message. Yet, it requires less power to be transmitted and can travel to much greater
distances. There are two types of FM signals: stereophonic and monophonic. Here
stereophonic is favored over monophonic, because it offers better sound quality.
Therefore, the design in hand utilizes FM stereophonic techniques to combine both the
left and right channels of the audio source and then transmits them to the receiver.
©2000 Nawaf Alshawwa All Rights Reserved
6
In this paper, a full design of a wireless stereo speakers system will be discussed
and explained in depth. The paper will contain a complete and general theory to describe
the design. The description part will include theory of the project, specifications, circuit
schematics, and block diagrams. The report will also include some economical analysis
explaining the cost of the design as a prototype and a retail product, as well as the person
hour labor and its cost. A time management Gantt Chart will show how long it took to
design and build each module, along with costs vs. time graph. A user manual was put
together for this product to help consumers understand and troubleshoot this electrical
device.
©2000 Nawaf Alshawwa All Rights Reserved
7
Wireless Stereo Speakers System Specifications
I.
Transmitter:
1.
Input Level range 0 ~ 50 milli VP-P from an audio source.  10 %
2.
Transmitter’s input impedance > 5 K  10 %.
3.
Two line level audio inputs at the transmitter (Left/Right).
4.
On/Off switch at the transmitter.
5.
Volume control at the transmitter.
6.
Balance Control at the transmitter.
7.
5 bands Equalizer at the transmitter.
a. 100 KHz  dB
(fl = 20 Hz & fh = 257 Hz)
b. 300 KHz  dB
(fl = 120 Hz & fh = 800 Hz)
c. 1 KHz  dB
(fl = 600 Hz & fh = 1.6 KHz)
d. 3 KHz  dB
(fl = 1.4 KHz & fh = 6 KHz)
e. 10 KHz  dB
(fl = 4 KHz & fh = 25 KHz)
8.
Frequency Modulation (FM) Stereo Transmission.
9.
Pre –modulation frequency range 20 ~ 53 KHz
(I)
L + R channel 20 ~ 15 KHz
(II)
L – R channel 23 ~ 53 KHz.
(III)
Pilot at 19 KHz
10.
Transmission Frequency 48 MHz (carrier).
11.
Range of operation 7 meters  23 ft.  10 %.
12.
Transmitter’s output power (FCC Regulations < 100 Milli Watts)
13.
Transmitter’s output impedance 50   10 %.
14.
Size: 9” W x 7” D x 4” H
©2000 Nawaf Alshawwa All Rights Reserved
8
II.
Receiver:
1. Right channel & Left channel speakers.
2. Receiver built in each speaker.
3. Output Load 8  speakers.
4. Output power 5 Watts RMS.
5. System’s bandwidth 20Hz – 15KHz.
6. Size: 8” W x 9” D x 9” H
III.
Miscellaneous:
1. Power supply 12 volts (AC outlet).
2. Operational temperature = Room Temperature
3. Mono-pole Antenna.
4. Antenna’s length (FCC Regulations < 1.5 meters)
Nominal = 15 cm.
©2000 Nawaf Alshawwa All Rights Reserved
9
Theory & Description of the Design
The Wireless Stereo Speakers System consists of two major modules: Transmitter
and Receiver. Each of these modules is composed of various other smaller modules. For
instance, the transmitter as shown in Figure 2, consists of a balance control, equalizer,
mixer, and modulator modules.
The transmitter is the main part of the design. The transmitter will be
hooked to an audio source. The signal will then be filtered to limit the frequencies
entering the circuit. This signal is then amplified in the pre-amp stage and put thorough to
the balance control to adjust the signal path. The equalizer comes in next, which will
fine-tune the signal. After the equalizer stage, the volume control stage is paced in order
to adjust the level of the signal. After this stage both the left and the right channels will
be combined in the mixer stage to produce the stereophonic signal. This stereophonic
signal will be modulated in the modulator module and passed to the power amplifier. At
the end, the power amplifier will transmit the signal through the antenna at a power level
that complies with the FCC regulation.
The receiver’s task is to detect the transmitted signal and pass it through to the
speaker. The process requires the following: the signal is picked up at the receiver’s
antenna. The antenna is then connected to an RF amplifier, which will emphasize on
selected frequencies around the carrier. The output is passed to the pre-amplifier to boost
up the level of the signal. Then the demodulator comes in next to recover the information
and separate the message from the carrier. Once the message is available, the stereo
decoder will separate the left and right channels and then put each to the designated
speaker, which will enable the listener to listen to the music.
©2000 Nawaf Alshawwa All Rights Reserved
10
48 MHz
CD Player
Left
Speaker
R - Channel
Transmitter
Right
Speaker
L - Channel
Figure 1: Layout of Wireless Stereo Speakers System
I.
Transmitter
The transmitter’s block diagram is shown in Figure 2 which consists of a balance
control, equalizer, mixer, modulator, and an output power amplifier which is connected to
the antenna. The transmitter is fed from a CD player, which supplies the audio signal that
will be modulated and transmitted. The input impedance of the transmitter is 20 K and
has an audio input level (sensitivity) that ranges from 0 ~ 50 milli VP-P. The output signal
of the CD player is already stereophonic, which means that the signal is separated into
two channels, a left and a right channel. The audio signal is passed through a low pass
filter before going to the pre-amp and the balance control network.
©2000 Nawaf Alshawwa All Rights Reserved
11
R
Audio
Device
L
Pre-Amp
&
Filter
Balance
Control
Trans.
Amplifier
Modulator
Equalizer
&
Volume
Mixer
Figure 2: Transmitter Block Diagram
The low pass filter will be set to roll off the signal at around 15 KHz before
entering the transmitter. This is necessary to eliminate beat frequencies that would be
caused by combining the 19 KHz from the audio source with the stereophonic pilot
signal. The stereo pilot is a signal at 19 KHz used to activate the receiver’s stereo decoder
circuit and also to identify the L+R from the L-R signals as shown in Figure 11. The low
pass filter will also insure that any unwanted frequencies beyond 15 KHz will not be
modulated and transmitted, since the bandwidth of the system is 20 Hz ~ 15 KHz. This
bandwidth is set to achieve high fidelity of the stereophonic system. A two-pole sallenkey low pass filter, which is a second order filter, is used in the design as shown in Figure
3. The output of the low pass is fed into the pre-amp, which will boost up the level of the
signal in order to equalize it. A printout of the simulation of the output of the filter is
provided in Figure 4.
©2000 Nawaf Alshawwa All Rights Reserved
12
0
C4
710p
R4
R5
U2
3
10k
+
V+
7
V+
10k
5
OS2
6
OUT
V6
2
0
-
LM741
V-
1
OS1
4 V-
C5
1500p
Figure 3: Low Pass Filter Schematics
600mV
Vmax = (499.977m)
(15.388K,353.600m)
400mV
200mV
0V
1.0Hz
V(U2:-)
10Hz
100Hz
1.0KHz
10KHz
100KHz
Frequency
Figure 4: Output of the low pass filter.
©2000 Nawaf Alshawwa All Rights Reserved
13
The Pre-amp to the transmitter is shown in Figure 5. This Pre-amp is built using a
wide band low noise operational amplifier, and designed to have a gain of 10 V/V. This
pre-amp has an input impedance greater than 5K, in order to shield and avoid any
loading from the pre-amp onto the input source (i.e. CD player). The output of the preamp is fed to the balance control and then to the graphic equalizer.
ROUT1
45k
RIN1
2
5k
V-
4
VSS
-
OS1
OUT
5
OS2
LF347
VCC
7
+
U6
6
V+
3
0
1
VINPUT3
0
Figure 5: Pre-amp Circuit
2.0V
(25.152u,0.9957)
Gain = 9.957 V/V
1.0V
(25.152u,100.061m)
0V
-1.0V
0s
20us
40us
60us
V(U6:+)
V(U6:OUT)
80us
100us
120us
140us
160us
180us 200us
Time
Figure 6: output simulation of the Pre-Amp
©2000 Nawaf Alshawwa All Rights Reserved
14
The balance control network will be controlling the input to the transmitter. The
balance control circuit is basically a switched circuit that allows specific inputs to pass
through a specific path as the user selects. It will balance control the left and the right
channels coming from the CD player. When the user selects the right channel for
instance, the balance control network will only allow the signal coming from the right
channel source to pass through. At the same time it will suppress the left channel signal
and ground it.
The balance network consists of two potentiometers wired in a center-tapped
manner as shown in Figure 7. This configuration will allow balance in the middle and
will also ground the unwanted signal by setting each of potentiometers to the desired
location. The network has high input impedance, in order not to overload the input
source. After the balancing module the signal is passed to the equalizer module.
Vleft
0
FREQ = 1k
VAMPL = 500m
VOFF = 0
Rleft
50k
0
Rright
50k
Vright
0
FREQ = 1k
VAMPL = 500m
VOFF = 0
Figure 7: Balance Control schematic
©2000 Nawaf Alshawwa All Rights Reserved
15
The graphic equalizer module is used to fine-tune the sound system. Equalizers
are used to flatten a system’s frequency response (making the levels the same at all
frequencies). In this design a graphic equalizer is used to fine-tune the sound signals. The
frequency range that the graphic equalizer operates at is 20Hz ~ 15KHz and it is divided
into 5 bands. These bands are chosen according to the center frequencies of the design,
which are 100Hz, 300Hz, 1KHz, 3KHz, and 10KHz. Each band will have a specific
bandwidth, the 3dB points which defines each bandwidth is listed below:
1. 100 KHz  dB
(fl = 20 Hz & fh = 257 Hz)
2. 300 KHz  dB
(fl = 120 Hz & fh = 800 Hz)
3. 1 KHz  dB
(fl = 600 Hz & fh = 1.6 KHz)
4. 3 KHz  dB
(fl = 1.4 KHz & fh = 6 KHz)
5. 10 KHz  dB
(fl = 4 KHz & fh = 25 KHz)
The first two bands and the last band are designed with quality factor (Q) of 0.5 to
cover a wide range of frequencies at beginning and end. The middle bands have Q = 1
which will be more narrow by definition than the earlier bands. By doing so, all the bands
will cover the entire bandwidth of the system as shown in Figure 9. In addition, each
band represents a set of sounds and instruments. The lower bands are for the bass, the
middle ones are for the human voice, and the higher bands are for the treble. The five
controls of the equalizer have a range of  10dB at each center frequency.
The layout of the graphic equalizer will be typically sliding controls arranged by
frequencies. Since the design is in stereo, the equalizer will have two inputs and two
outputs. The stereo equalizer controls the whole system (both the left and right channel).
Typically frequency bands of a graphic equalizer overlaps. This overlapping ensures
better sound quality.
©2000 Nawaf Alshawwa All Rights Reserved
16
10k
-
OS1
10k
1Vac
0Vdc
OUT
3
+
10k
V+
R58
OS2
12
V8
10k
Vin
5
0
0
U15
7
V7
-12
1
6
Vn
uA741
2
Vp
4
0
Vp
V-
uA741
2
V-
R56
4
Vn
V6
-
Vn
1
OS1
10k
0
6
500
3
10k
500
R65
25k
+
OS2
5
L1
3
7
Vp
1st Fo =100Hz
4
+
OS2
5
L2
10m
3rd Fo =1KHz
3
0
Buffer
500
L3
10m
U20
OS1
10k
OUT
3
Vp
0
+
OS2
U21
6
5
Vin
L4
10m
Vp
uA741
2
4
R81
1
Vn
-
V-
4
Vn
-
V-
uA741
2
OS1
10k
OUT
3
0
+
V+
5
Vin
OS2
1
6
5
L5
10m
U22
Vp
7
OS2
R80
6
V+
V+
+
500
1
7
OS1
OUT
0
Vp
4
-
V-
Vn
10k
3
25k
+
U19
0
0
25k
33u
2nd Fo =300Hz
38
4th Fo =3KHz
0.22u
5th Fo =10KHz
26.7n
1.256k
0
Vn
OS1
OUT
10k
7
Vin
uA741
2
-
3.3u
69
500
R79
uA741
2
10k
Vp
12.57
25k
Summer
10k
6
U18
0
220u
OS1
OUT
10m
U17
0
Vin
-
10k
0
1
4
3
6
uA741
2
Vp
V-
OUT
R67
V-
10k
1
V+
OS1
7
-
Vn
V+
4
Vn
V+
Vin
uA741
2
5
OS2
U16
5k
V-
R66
+
7
25k
7
R61
V+
OUT
220
0
0
Figure 8: Graphic Equalizer Schematic
©2000 Nawaf Alshawwa All Rights Reserved
17
OS2
1
6
5
Vout
Fc = 300. 339
6. 0V
Fc = 1. 0240K
Fc = 3. 0034K
Fc = 100. 000
Fc = 10. 089K
4. 0V
2. 0V
0V
1. 0Hz
V(R68: 2)
10Hz
V(R76: 2)
100Hz
1. 0KHz
V(C21: 1) V(R77: 2) V(R67: 1)
Frequency
10KHz
100KHz
Figure 9: Graphic equalizer spectrum
At the output of the equalizer a volume control is designed to adjust the volume of
the signal up to +10 dB this network is shown in Figure 10. This network consists of a
potentiometer, which controls the level of the signal. When the potentiometer is set to
have a maximum resistance, the volume is turned down and when it is set to have a
minimum resistance, the volume is turned up.
INPUT FROM
GRAPHIC
EQUALIZER
R Volume
50k
0
Figure 10: Volume control network
©2000 Nawaf Alshawwa All Rights Reserved
18
After Equalizing the signals to the selected range of frequency preference, both
output of the graphic equalizer (left and right channels) must be combined in order to
transmit the signals in FM stereo mode.
The mixer is the network that will combine both left and right channels of the
signal in a suitable way for stereo transmission. With stereophonic transmission, the
information signal is spatially divided into two 20Hz ~ 15 KHz audio channel as
mentioned earlier (a left and a right). The spectrum of the stereophonic transmission is
shown in Figure 11, which has two channels (1) the left plus right channel (L + R), (2)
the left minus right channel (L - R). The L + R stereo channel occupies the 0 - 15 KHz
baseband. The L – R channel amplitude modulates a 38 KHz subcarrier and produce the
L – R stereo channel, which is a double-sideband suppressed carrier (DSB-SC) that
occupies the 23 – 53 KHz passband, used only for FM stereo transmission. A regular
mono receiver can demodulate the whole spectrum but only the 20- 15 KHz (L + R)
channel is amplified and fed to the speakers. A special stereophonic receiver must be
used to listen to the whole FM stereo spectrum, which will be discussed in next few
pages of the report.
©2000 Nawaf Alshawwa All Rights Reserved
19
L+R
Stereo
Channel
Stereo
Pilot
L – R Stereo
Channel Subcarrier
L+R
0
15 19
23
(LSB)
(USB)
LR
LR
38
53
f (KHz)
Figure 11: FM Stereo Spectrum
In the mixer module shown in Figure 12, the left (L) and the right (R) channels
are combined in a linear matrix network. The linear matrix network will produce the L +
R audio signal and the L – R audio signal by inverting the R signal and adding to it the L
signal. Now, the L + R and L – R are signals in the audio band and must be separated
before modulating the carrier for transmission. This is achieved by translating the L – R
audio signal up the spectrum as shown in Figure 11. The translation is done by using the
L – R audio signal to modulate a 38KHz subcarrier in a balanced modulator to produce a
DSB-SC. Also, for demodulation purposes, a 19 KHz pilot is transmitted rather than the
38 KHz subcarrier because it is more difficult to recover the 38 KHz in the receiver.
Dividing the frequency of the subcarrier produces the 19-KHz pilot. This frequency fits
between the L + R and DSB-SC L – R signals as shown in Figure 11. To conclude the
mixer’s role, all three signals are added together to form the composite stereo band
signal, which will be fed to a low pass filter design to roll off at 63-KHz to get rid of the
©2000 Nawaf Alshawwa All Rights Reserved
20
unwanted frequencies. The Composite stereo band signal is then fed to the FM modulator
where it modulates the main carrier.
R - CH
Matrix
L - CH
L+R
LPF
Balanced
Modulators
Composite
Baseband
Signal to FM
Modulator
L-R
DSB - SC
2
38 KHz
38 – KHz
Oscillator
Figure 12: Mixer Module
The circuit that does all of the above tasks is shown in Figure 14. And as
explained earlier, this circuit adds L+R, L-R, and the 19KHz pilot to modulate the carrier
signal for transmission. This Mixer circuit consists of three low noise operational
amplifiers (SA/NE 5532), and a balanced modulator (LM 1496N) as shown in Figure 11.
The main purpose of the Op-Amps is to add, subtract and buffer parts of the signals. The
first op-amp inverts the right signal and adds it to the left signals (L-R) as labeled in
Figure 14. This output is fed into the (LM 1496N) to amplitude modulate the 38KHz subcarrier. The output on the (LM 1496N) is passed through a low pass filter that has a cut
off frequency of 63KHz to get rid of the unwanted RF noise, and then passed through a
buffer to shield it from the end stage of the mixer circuit. The end stage is an op-amp that
©2000 Nawaf Alshawwa All Rights Reserved
21
adds all the signals to form the composite stereo signal, which is then fed into the
modulator stage to modulate the 48MHz carrier. The mixer circuit required two sine
waves to synchronize the operation of the modulator and to help the receiver recover the
stereo information. Those signal sine waves are at 38 KHz and 19 KHz, they are
produced using the circuit in Figure 13. The oscillator circuit consists of a number of
inverters (74HC04), a reset D flip-flop (74HC74), two operational amplifiers (NE/SA
U1A
1
U1A
2
1
U1A
R2
2
1
3
74 HC0 4 10 0k
1k
OS1
5532 OUT
+
OS2
1
6
5
38 KHz Sine Wave
U2
74 HC0 4
VCC
7
74 HC0 4
2
-
V+
2
V-
4
5532), and a 38Khz crystal.
75 - 4 00 pF
Trim for Peak
0.00 12u F
10 m
74 HC0 4
22 0pF
U1A
X1
2
0
0
0
R1
4
+1 2V
14
2
3
56 pF
C
R
S
4
D
6
0
0
Q
Q
5
OS1
5532 OUT
1
2
-
3
10 0k
0.00 75u F
+
OS2
1
6
5
19KHz Sine Wave
U2
VCC
7
25 pF
51 0k
74HC74
38 Khz
V-
1
V+
1M
75 - 4 00 pF
VCC
10 m
Trim for Peak
7
12
0
0
0
Vss
V3
-1 2
0
Figure 13: Sine Wave Oscillator
©2000 Nawaf Alshawwa All Rights Reserved
22
V3
0
VCC
12
VSS
V2
-12
V3
0
0
R2 10k
RIGHT1
2
-
10k
LEFT1
OS1
5532 OUT
3
+
V+
From
Audio
LPF
V-
4
VSS
OS2
1
6
L-R
5
10k
7
VCC
10k
10k
10k
0
2
-
OS1
10k
Pilot Signal
19Khz Sine wave
5532 OUT
3
100k
+
V+
VCC
V-
4
VSS
OS2
Composite Stereo
Signal
1
6
L+R+19K+38K
5
7
VCC
1k
5k
10k
0
500
0.1u
8
51
10k
10k
200
51
50k
0
1k
2
3
VCC
Balanced
6
10 Modulator
4
12
LM 1496N
1
14 Pin
DIP
VCC
3.9k
3.9k
20k
0.01u
VSS
10m
10m
51
2
0
Carrier Level
6.8k
38Khz
Subcarrier
Level
4
0
0
0.0012u
0.0024u
0.0012u
0
0
0
V-
0.1u
-
OS1
5532 OUT
3
+
OS2
1
6
5
VCC
7
1k
V+
38Khz
Sine
Wave
1k
VSS (-12V)
0
0.1u
D1N5237
0
0
2.2k
0
Figure 14: Mixer of Left and Right Channels
©2000 Nawaf Alshawwa All Rights Reserved
23
Frequency modulation (FM) is used in this design. This modulation is done in the
modulation module, which modulates a 48-MHz carrier with composite stereo band
signal. Standard FM transmitters use a Voltage-Controlled Oscillator to produce FM
signals. A buffer to provide isolation and therefore better oscillator frequency stability
follows the VCO. The MC1648 is one suitable IC chip for this modulation. It utilizes a
tank circuit to set the frequency of operation as shown in Figure 15.
The tank circuit is a parallel combination of a capacitor with an inductor, which
both are chosen upon deciding the center frequency of the design. These values can be
calculated with f0 = 1 / (2*(LC)^1/2). The bandwidth of this signal can also be calculated
from BW = (f0 / Q) where Q is the quality factor. This quality factor determines the 3dB
point of the resonant circuit.
A varactor diode is incorporated into the tank circuit to provide voltage variable
input for the oscillator (VCO). As shown in Figure 15, the 1K resistor is added at the
input to protect the varactor during the operation. This resistor is may be removed if the
dc input voltage does not cause the diode to become forward biased. Also, 0.1uF
capacitors are placed to bypass the VCO input (varactor diode), guaranteeing only dc
levels at this point. The FM signal is then amplified up to its final output power by power
amplifiers and their driver amplifiers.
©2000 Nawaf Alshawwa All Rights Reserved
24
Vin
MC1648
0.1uF
10
0
L
0.15uH
1k
3
12
D
MV2106
5
C1
0
Tank Circuit
Rvar
C2
0.1uF
0
0
Figure 15: Voltage Controlled Oscillator.
The transmitter’s output stage is a class AB power amplifier. This power
amplifier is designed to transmit the composite signal at a very low power that is set by
the FCC regulations (< 100 mWatts). This design is shown in Figure 16, which is a
typical class AB, it is characterized over the other classes by having minimal to none
cross over distortion. This characteristic is very important in stereo FM transmission,
because the receiver will distort and will have problems with decoding the signal.
©2000 Nawaf Alshawwa All Rights Reserved
25
V+
232
RB1
Q1
TIP31A
D5
D1N4002
1
Antenna
VINTRANS1
D6
D1N4002
1
ROUTTRANS1
50
TIP32A
0
0
Q3
232
RB2
V-
Figure 16: Transmitter’s Power Amplifier
II.
Receiver (L & R Speakers)
An FM waveform carries its information in the form of frequency, so that the
amplitude is constant. FM stereo receivers are identical to standard FM receivers up the
output of the audio detector stage. There are several methods for demodulating a FM
signal such as phase-locked loop (PLL) demodulator, slope detection/FM discriminator,
and quadrature detector. In this design, a PLL demodulator is used to recover the audio
signals. This particular method is chosen because PLL is the best method conceptually
for demodulating a FM signal. The output of the PLL will be put through the decoder to
©2000 Nawaf Alshawwa All Rights Reserved
26
separate the left and right channel. At the end, each channel will be put through to a
power amplifier stage to drive the designated speaker.
RF
Pre-amp
Demodulator
Stereo
Decoder
Audio
Amplifier
Figure 17: Receiver Block Diagram
The RF Pre-amp stage is the most important stage of the receiver’s module, since
it’s the one that tunes in for the RF signals coming from the transmitter. The antenna
picks up signal from the air and passes them to the RF Pre-amp. The RF Pre-amp boosts
up the weak signal from the antenna, and tunes to the desired frequency or reception. It
also prevents the demodulator’s input from being coupled to the antenna, where it could
be radiated into space. The RF Pre-amp usually has tank or a resonator circuit, which is a
parallel LCR that is designed to tune in to a specific frequency, this frequency in this
design in the carrier frequency, which is at 48MHz.
The RF amplifier (preselector) shown is Figure 18 was incorporated from a book
called “Secret of RF Circuit Design”. This circuit has a very high sensitivity, which is the
©2000 Nawaf Alshawwa All Rights Reserved
27
ability to pick up weak signals from an antenna. The main job of JFET active preselector
circuit is to separate two closely spaced signals, and to reject unwanted signals that are
not on or near the desired frequency being tuned. The preselector uses the common gate
configuration where the signal is applied to the source and the output is taken from the
drain. The tuning will be done using the variable capacitor (Cvar), as shown in Figure 18.
The output of the signal will be amplified and fed to the demodulator to recover the
information sent by the transmitter.
VCC
C6
0.01 u
0
R2
27 0
C5
0.01 u
0
L3
10 0u
C2
J1
FN43 93
0.00 1u
C3
0.00 1u
VOFF = 0
VAMPL = 1 0m
FREQ = 48meg
Vinp ut
L1
Cva r
10 uH
36 5p
R1
15 0
C4
1n
Lo ut
10 uH
0
0
Figure 18: RF amplifier (preselector)
A FM demodulator produces an output that is proportional to the instantaneous
frequency of the input. As mentioned earlier in the report phase-locked loop
demodulation circuitry is used in this design. Phase-locked loop is a feedback circuit,
which tries to match a local oscillator to the modulated carrier frequency. A PLL consists
of thee major components: a phase detector, a loop filter, and a voltage controlled
©2000 Nawaf Alshawwa All Rights Reserved
28
oscillator (VCO) connected together in the form of a feedback loop as shown in Figure
20. The VCO is a sine-wave generator whose frequency is determined by a voltage
applied to it from an external source. The loop is said to be phase locked when the VCO
frequency f0 and the loop input signal frequency fi are identical (f0=fi), and only if a phase
difference exits between the VCO and the input signal.
90k
490k
VSS
RIN2
2
OS1
0
+
V+
OUT
3
OS2
1
0
10k
6
3
7
VOFF = 0
VAMPL = 100u
FREQ = 20k
+
OS2
5
10k
0
100k
VCC
3
100n
5
-
OS1
OUT
C1
6
LM741
LM741
VCC
OUT
V+
10k
-
OS1
7
2
V-
RIN4
-
1
+
V+
2
OS2
1
Vout
6
5
LM741
7
RIN3
4
VSS
V-
4
VSS
V-
4
390k
100k
VCC
U6
U7
0
U8
0
V6
VCC
10k
VSS
V4
12
0
V5
-12
0
0
Figure 19: Receiver. Pre-Amp
Input Signal
Phase Detector
Vd
Loop Filter
Vo
Amp
fi,i
f0, 0
VCO
Free- running
frequency
Figure 20: PLL Block Diagram
©2000 Nawaf Alshawwa All Rights Reserved
29
After the demodulation stage, the stereo decoder comes in place. Its main job is to
process the baseband signal and separate the L and R channels and feed them to the
designated speaker. In receiver’s stage the operation of the decoder is opposite to that of
the mixer in the transmitter’s stage. The composite baseband signal consists of the L + R
audio channel, L –R audio channel, and the 19-KHz pilot. Those channels are separated
from the composite baseband signal with filters as shown in Figure 21. The 19 KHz is
filtered with a high-quality factor (Q) band-pass filter, multiplied by 2, and fed to the L –
R demodulator. The L + R stereo channel is filtered off by a low-pass filter with an upper
cutoff frequency of 15 KHz. The L – R double-sideband signal is separated with a
broadly tuned band-pass filter and then mixed with the recovered 38 KHz carrier in a
balanced modulator to recover the L – R audio information.
Frequency
Demodulator
Composite
Low-pass filter
Cutoff @ 15KHz
2R
Matrix network
(Stereo decoder)
L+R
2L
Baseband signal
L-R
Band-pass filter
23-53 KHz
19 KHz
Band-pass filter
L–R
Balanced
product
demodulator
Sidebands
19 KHz
Pilot
Amplifier and
(X2) multiplier
38 KHz
subcarrier
Figure 21: FM stereo decoder
©2000 Nawaf Alshawwa All Rights Reserved
30
VCC
GND
11
Divide f
by 2
(38KHz)
Divide f
by 2
(19KHz)
Divide f
by 2
(19KHz)
13
Power
supply
regulator
12
L.D
.
15
VCO
16
Schmitt
trigger
19KHz
phase
detector
P.A
19KHz
pilot
presence
detector
9
Matrix
R
14
1
L
10
38KHz
(L-R)
detector
CA 3090
2
3
4
5
6
7
8
L.D = lamp drive
P.A = Pre-amp.
VCO = voltage controlled oscillator
This chip is used to decode the FM stereo signal. It uses a phase-locked loop to
achieve subcarrier frequency coherency for demodulation of the L-R signal. It also uses a
76KHz VCO, and a divide by 2 (2) flipflops network to provide a 38KHz subcarrier to
synchronize the L-R product detector for demodulation of the DSB-SC. Another (2)
flipflop is used to divide the 38KHz down to19KHz for input to the phase detector. The
PLL loop gain is high enough here to achive a low phase error. The ouput of the 38KHz
L-R detector is combine with the L+R in the matrix netework to produce the left, and
right channel seperatly. This proceure is as following:
(L+R) – (L-R) = 2R and (L+R) + (L-R) = 2L
©2000 Nawaf Alshawwa All Rights Reserved
31
the number 2 in the (2R) and (2L) indicates only the amplitude of each signal. At the
output of each channel there is a deeemphasis network which will recover the preemphasis of the higher frequencies in the transmitter.
Input Number
Description
1
Composite FM detected signal input
2
Bypass
3
Ground
4
Ground
5
Ground
6
RC Network
7
19KHz Pilot lamp
8
Sensitivity network
9
Left output Channel
10
Right Output Channel
11
+ Vcc
12
Lamp Drive circuit
13
Ground
14
Phase lock loop filter network
15
Capacitor network 76KH Network
16
Indicator input 76KHz
Table 1: CA3090 Pinouts
©2000 Nawaf Alshawwa All Rights Reserved
32
The matrix network combines the L + R and L – R signals in such a way as to
separate the L and R audio information signals. Which are then fed to their respective
Deemphasis networks and speakers as shown in Figure 22.
LR
Matrix Network
L+R
2L
Deemphasis
Network
Audio
Amp
2R
Deemphasis
Network
Audio
Amp
Left
Speaker
Right
Speaker
Figure 22: Stereo matrix network Decoder
The Receiver’s output stage is a class AB power amplifier. This power amplifier
is designed to drive an 8-ohm speaker load and produce 5-Wattsrms. This design is shown
in Figure 23, which is a typical class AB, it is characterized over the other classes by
having minimal to none cross over distortion. The output of this power amplifier will
have a voltage swing of about 9 Vp, this will ensure that we are getting the full range and
maximizing the sound quality of the speaker. The speakers following this stage are of the
full range type with an outer diameter of 120X60 (mm).
©2000 Nawaf Alshawwa All Rights Reserved
33
VCC
R1
54
Q2
TIP31A
D1
D1N4002
RE1
0.5
RE2
0.5
D3
D1N4002
ROUTREC1
8
TIP32A
0
Q4
R7
54
Vss
Figure 23: Receiver Power amplifier.
©2000 Nawaf Alshawwa All Rights Reserved
34
Physical Layout of the Project
I.
Transmitter:
Front & Side View
+ 10 dB
Balance
4”
L
Volume
R
0
Power
+10dB
- 10 dB
7”
9”
Rear View
Audio Plug in
L
R
©2000 Nawaf Alshawwa All Rights Reserved
35
II.
Receiver: (Left & Right Speakers)
Front & Side View
9”
Tune
9”
8”
Input Connector:
L. Ch
To
Transmitter
From
CD Player
R. Ch
Figure 24: Connector Headphone to Y- Adapter
©2000 Nawaf Alshawwa All Rights Reserved
36
History of the Project
The project has gone through some changes in the designing phase. These
changes came about when a problem was faced or when an enhancement was considered
necessary in some parts of the design.
In the beginning, infrared techniques were considered for use in modulation and
transmission of the information. After careful review and study of the infrared, many
drawbacks were noticed, such as, direct line of sight, short propagation distance, and
susceptible to light interference. For that the design took a different route. This route was
to use frequency modulation techniques to modulate the carrier signal and transmit the
information to the receiver.
In the proposal phase, all the efforts were put into figuring out the whole design
and integrating the ideas together. On the other hand from an economical point of view,
the hours of labor were standing at 576.5 hrs, and the actual cost of the prototype was
equal to the estimated prototype cost
Between the proposal and the preliminary design review, minor changes were
done to the design. The distance of operation was increased from 3 meters to 7 meters.
The economical picture of this phase was relatively good, because the hours of labor
were reduced by 18.5 hours, which eventually brought down the actual prototype cost by
$1626.
After the preliminary design review the project entered the critical phase. In this
phase, not many changes were done to the design. This phase was being used to figure
out and order the parts that were going to be used in the project, such as the, modulator,
©2000 Nawaf Alshawwa All Rights Reserved
37
demodulator, and stereo decoder. At this stage, the hours of labor were cut down slightly
by 8 hours. This reduction brought down the actual prototype cost by $112.
In the final design review, some changes were made to the design. After
simulating and building the graphic equalizer, it was verified that this design was no good
for this project because it was not working according to the specification. Therefore, a
new design was established to replace the old graphic equalizer. The new design was
simulated to verify its right operation, and make sure that it complies with the
specifications. From an economical prospective, the hours of labor were cut down by 10
hours from the last critical design review phase, and in total they were reduced by 36.5
hours. Eventually, this has brought down the total cost of the prototype by $2,302.
©2000 Nawaf Alshawwa All Rights Reserved
38
Test of Design
The Design consists of two major modules: transmitter and a receiver. Those
modules include smaller modules within them, such as modulator, demodulator, filters,
and mixers. To test the overall performance of the Wireless Stereo Speakers System,
various things are needed such as a CD player, headphone jack Y-adapter, and an AC
outlet (110 VACr.m.s @ 60 Hz). The user will plug one end of the adapter into the CD
player, and the other end into the transmitter. Each device requires a single AC outlet to
power it up. When all of the above are ready then the transmitter will be enabled and it
will transmit the information from the CD player to the speakers.
Testing the project during design and building periods, a couple of equipment are
needed such as a Lambda source power supply to power up the circuits, an oscilloscope
to view the signals, and a function generator to supply the circuits with a defined
sinusoidal signal. A spectrum analyzer is also needed here to view the fundamental
frequencies of the transmitter and the receiver. This will enable the test engineer to check
the operation of each module and make sure they work accordingly to the specification
defined earlier in the report. The lab equipment are sufficient enough to enable any
design, test engineer to make any measurement on a specific circuit
©2000 Nawaf Alshawwa All Rights Reserved
39
Parts List
Part Name
OR Number
SA 5532A
CA3090
LM1496N
Resistor
47 uF (10V)
10 uF (10V)
TO-92 N-CH JFET
Toroids
Capacitor
UA741CN
Crystal
Choke
LF347
MC1648
Tip31A
Tip32A
NE568AD
Choke
Casing
Speakers
Skirted round knob
potentiometers
Description
Dual low noise Op-Amp.
Stereo Decoder
Balanced Modulator
1/4 Watt (Various Values)
Capacitor (Aluminum Electrolytic)
Capacitor (Aluminum Electrolytic)
N-Channel JFET
Toroids
Ceramic Disc (Various Values)
General Purpose Amp 8-Dip
Overtone (Various Values)
RF choke 1000uH
Wide bandwidth JFET OP-Amp
Voltage Controlled Oscillator
Meduim Power Amplifier-NPN
Meduim Power Amplifier-PNP
Phase-Locked Loop
RF Choke 10uH
Shielded Boxes
Oval Magnetic Shielded Speakers
Instrumentation Knobs
12mmDual Potntiometers
Manu- Vendor
facturer
Phillips Arrow
RCA
NTE
National NTE
Mouser
Mouser
Mouser
Mouser
DigiKey
Mouser
Newark
DigiKey
DigiKey
National DigiKey
Motorola
mouser
mouser
Phillips Newark
Mouser
Sescom
DigiKey
Keystone DigiKey
Panasonic DigiKey
Vendor Part
number
NE5532An
NTE789
NTE973D
29SJ250-(value)
75-515D10V47
75-515D10V10
526-NTE312
M5701-ND
140-CD302U9-xxxM
UA741CN
CTX***-ND
M5258-ND
LF347M-ND
511-TIP31A
511-TIP32A
NE568A
M5258-ND
TBD
P10187-ND
8554K-ND
P2B6503-ND
TOTAL
Price
Q
Cost
@ (quantity)
$0.86 @(1+)
6 $5.16
$11.35 @(1+)
1 $11.35
$3.20 @(1+)
1 $3.20
$0.009 @(200) 200 $1.80
$0.05 @(250)
10 $0.50
$0.05 @(250)
10 $0.50
$1.34
2 $2.68
$3.50
3 $4.02
$0.36 @(200)
40 $14.40
$0.26 @(500)
10 $2.60
$3.41
3 $10.23
$3.27
2 $6.54
$0.96 @(100)
2 $1.92
$4.48
1 $4.48
$0.46 @(100)
2 $0.92
$0.46 @(100)
2 $0.92
$1.41
1 $1.41
$3.27
2 $6.54
TBD
TBD
$6.05
2 $12.10
$3.38
$13.52
$1.99
5 $9.95
$105.60
IP = In Possession, OO = On Order, NO = Not Ordered
Table # 5: Parts List
©2000 Nawaf Alshawwa All Rights Reserved
40
Status
IP
IP
IP
IP
IP
IP
OO
OO
IP
IP
OO
IP
IP
NO
IP
IP
NO
IP
NO
NO
NO
IP
Conclusion
As of today the project is on track. The projected completion date is still April 29,
2000. Phase one of the project, described as the design, is coming to a close with the final
design review (FDR). The new phase, which requires actually building the project, is
scheduled to begin with Project Report # 1 on December 2nd, 1999.
Problems were faced in the graphic equalizer’s design, were solved by designing
a new equalizer shown in Figure 8. Presently, efforts are being made in order to conduct
early building and testing procedures, so that the final design may be ensured. Most of
the designs have been completed and verified using OrCAD; the ones not yet completed
are not verifiable because of the lack of parts found in OrCAD. To date, almost all the
parts have been ordered and are on their way. Starting next week the building phase
should begin as projected in the Gantt charts.
At this time the retail price of the project is still standing at $ 190. Labor hours
have been reduced by 36.5 hours from the initial estimated hours (from 588.5 to 552
hours). In addition, the total cost of the prototype has been reduced by $2302 from the
original estimated price (from $46,418 to $44,116).
©2000 Nawaf Alshawwa All Rights Reserved
41
References
Young, Paul H. Electronic Communication Techniques, 4th Edition. New Jersey:
Prentice-Hall, Inc. 1999.
Carr, Joseph J. Secret of RF Circuit Design, 2nd Edition. Washington, D.C: TAB Books,
1997.
Roddy, Dennis and Coolen, John. Electronic Communication, 3rd Edition. Virginia:
Reston Publishing Company, Inc. 1977.
Sedra, Adel and Smith, Kenneth. Microelectronic Circuits, 3rd Edition. New York:
Oxford University Press, 1989.
Haykin, Simon. Communication Systems, 2nd Edition. New York: John Wiley and Sons,
1978.
Motorola, Website: http://www.motorola.com
Minicircuits, Website: http://www.minicircuits.com
Phillips semiconductor, Website http://www-us.semiconductors.philips.com/
Silverman, Joseph R. The George Washington University. School of Electrical and
Computer Engineering.
Doroslovacki, Milos. The George Washington University. School of Electrical and
Computer Engineering.
©2000 Nawaf Alshawwa All Rights Reserved
42
Appendix - B
(User Manual)
+
B 10
4 Lal RdB
” a
n
ce 10
dB
V
0ol
u
m
e
P
o
w
er
T
u
ne
©2000 Nawaf Alshawwa All Rights Reserved
43
User Manual
I.
Description of the Product:
The Wireless Stereo Speakers System is a luxury piece of equipment that can be
used in the house, office and outdoors too. This system consists of three modules:
transmitter, right speaker, and left speaker. Each of these modules operates from an AC
outlet using an AC to DC power transformer. This devise will let the listener enjoy his or
her favorite music in many parts of the house, office, or outdoors without having string of
wires hanging all around the place.
The Wireless Stereo Speakers System connects to the CD player, and transmits
the music in the form of RF signals. These signals will be picked up at each receiver and
put to the speakers so that everyone around will be able to listen to the music without
having to be constrained to the length of wires and messiness. The transmission
frequency for the wireless stereo speakers is 48 MHz. The stereo speakers will pick up
the transmitted signal up to 23 feet (10 %) away.
©2000 Nawaf Alshawwa All Rights Reserved
44
II.
List of Specification of the Product:
1. Transmitter:
1. Input from an audio source.
2. Input Level range 0 ~ 50 milli VP-P.
3. Transmitter’s input impedance > 5 K  10 %.
4. Two line level audio inputs at the transmitter (Left/Right).
5. On/Off switch at the transmitter.
6. Volume control at the transmitter.
7. Balance Control at the transmitter.
8. 5 bands Equalizer at the transmitter.
a. 100 KHz  dB
b. 300 KHz  dB
c. 1 KHz  dB
d. 3 KHz  dB
e. 10 KHz  dB
9. Frequency Modulation (FM) Stereo Transmission.
10. Pre –modulation frequency range 20 ~ 53 KHz
I. L + R channel 20 ~ 15 KHz.
II. L – R channel 23 ~ 53 KHz.
III. Pilot at 19 KHz.
11. Transmission Frequency 48 MHz (carrier).
12. Range of operation 7 meters  23 ft.  10 %.
13. Transmitter’s output power (FCC Regulations < 100 Milli Watts)
Nominal = 10 Milli Watts.
©2000 Nawaf Alshawwa All Rights Reserved
45
14. Transmitter’s output impedance 50   10 %.
15. Size: 9” W x 7” D x 4” H
2. Receiver:
1. Right channel & Left channel speakers.
2. Receiver built in each speaker.
3. Output Load 8  speakers.
4. Output power 5 Watts RMS.
5. System’s bandwidth 20Hz – 15KHz.
6. Size: 8” W x 9” D x 9” H
3. Miscellaneous:
1. Power supply 12 volts (AC outlet).
2. Operational temperature = Room Temperature
3. Mono-pole Antenna.
4. Antenna’s length (FCC Regulations < 1.5 meters)
Nominal = 15 cm.
©2000 Nawaf Alshawwa All Rights Reserved
46
III.
How to use the Product:
The wireless stereo speakers system is a very simple device to operate. Simple
connect all the device: the transmitter, left and right speakers to an AC power outlet using
the AC to DC power transformer provided in your purchase. Then connect the CD player
to the transmitter-using headphone to Y-adapter. Each end of the Y-adapter connects the
rear of the transmitter, in the order shown in the Figure below.
L. Ch
To
Transmitter
From
CD Player
R. Ch
Figure: Headphone to Y-adapter connection.
The Speakers can be placed within the range given in the specification. Make sure
to put the right speaker on the right and left speaker in the left to get the maximum sound
fidelity and quality. After all that, you can turn the transmitter ON/OFF using the power
button on the front of the transmitter. You can also, adjust the volume and the level of
signals using the volume control and the graphic equalizer controls on the front of the
transmitter too. Incase the signal is not clear, there is a tune knob on each speaker that
enable you to adjust the reception of each receiver until the signal becomes audible.
©2000 Nawaf Alshawwa All Rights Reserved
47
VI. Maintenance Procedures:
The wireless stereo speakers system is made of very sensitive devices and should
be treated with good care. They should not be applied to extreme temperature or pressure.
To ensure a long life for your system, you must follow these instructions:

Before connecting any inputs to the transmitter be sure to turn the device off first.

Do not put a flower vase filled with water or any small metal objects on the
transmitter and the receiver.

Exterior influences such as lightning and static electricity can affect the normal
operation of your wireless stereo system. If this occurs, turn the transmitter off and on
again using the power button on the front panel of the transmitter. Or disconnect and
then reconnect the AC power cord to the AC power outlet.

For safety precautions:
-
The units are to be used only where the power supply is AC 120 V, 50 –
60Hz, it cannot be used anywhere else.
-
To prevent electric shock, match the wide blade of the AC power plug to the
wide slot, and fully insert.
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When opening the cabinet, be sure to disconnect the AC power plug from the
AC outlet.
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Wipe the cabinet with a soft cloth when cleaning.
IV. Trouble-Shooting Procedures:
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The wireless stereo speakers system is sensitive to harmful interference. It
interference is detected, then it is from a nearby source. In a case of interference bring the
units as far as possible from the source of interference. Sources of interference’s can be
other transmitters nearby, or high voltage transmission lines.
In the case of malfunctioning, reset the system by turning the devices off and back
on to check their operation status. If the problem persist, unplug the AC power cord from
the AC power outlet. Open the cabinet of the transmitter and check for any lose
components, if any found close the cabinet again and send your product back to us and
we will gladly fix it for you.
In case of unclear sound at any of speakers. You may solve the by tuning the
devices using the tune knob on the front panel of the speaker. If the problem did not go
away, try getting the speakers closer to the transmitter. If this problem persist send your
product back to us and we will gladly fix it for you.
©2000 Nawaf Alshawwa All Rights Reserved
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Appendix - C
(Data Sheets)
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Appendix - D
(Log Book)
©2000 Nawaf Alshawwa All Rights Reserved
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