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Appliances Control Using Mobile Phone (DTMF)

THESIS · JUNE 2010

DOI: 10.13140/2.1.1235.2969

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1 AUTHOR:

Manhal Jaafar Jaber Alhilali

Universiti Teknologi Malaysia

1 PUBLICATION 0 CITATIONS

SEE PROFILE

Available from: Manhal Jaafar Jaber Alhilali

Retrieved on: 19 March 2016

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University of Omer Al-Mukhtar

College of Engineering

Electrical and Electronics Engineering Department

Appliances Control Using Mobile Phone

A Project Submitted in Partial Fulfillment of the Requirement for the

Bachelor Degree (B.Sc.) in Electrical and Electronic Engineering

By

Manhal J. Alhelaly

Supervisors

Dr. Ayad A. Mousa

Mr. Abdelhamid M. Raheel MSc.

June, 2010


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Acknowledgment

To my supervisors:

Dr. Ayad A. Mousa

Mr. Abdelhamid M. Raheel

You learn me how to do it, I will be forever thankful,,,


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Contents

Title Page No.

Abstÿÿract VII

Chapter 1

Introduction

1.1 System Overview 2

1.2 The System Features 3

1.3 The System Description 3

Chapter 2

DTMF Detection Unit

2.1 DTMF Signaling 4

2.2 DTMF Detection 6

2.2.1 DTMF Decoder Specifications.1 6

2.2.2 DTMF Detection Methods 8

2.3 The Integrated DTMF Decoder 10

2.4 The Control Unit Interfacing 14

Chapter 3

Control Unit

3.1 Device Switching Section 16

3.2 Device Status Feedback Section 18

3.2.1 The Feedback Circuitry 18

3.2.2 Beep Tone Generator 19

3.3 Relay Drive Circuit 19


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Title Page No.

Chapter 4

Overall System Design and Practical Work

4.1 System Operation 21

4.2 The System Block Diagram 22

4.3 The DTMF Detection Unit 23

4.4 The Control Unit 24

4.5 The Practical Work 27

Chapter 5

Conclusions and Future Work

5.1 Conclusions 29

5.2 Future Work 29

References 30

Appendices

A ITU-T Q-24 Recommendations

B Background: Gortzel Algorithm

C CM8870 Data Sheet


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List of Figures

Figure No. Title Page No.

1.1 Home automation system 1

1.2 Applinaces control using mobile phone 2

2.1 Telephone keypad matrix 5

2.2 DTMF signal of key number “3” [697,1477] Hz 5

2.3 The DTMF detection secheme 8

2.4 Flow chart for the DTMF detector using Goertzel

Algorithm

11

2.5 The Block Diagram of CM8870 13

2.6 Block Diagram of the decoder chip 74154 14

3.1 3 state buffer symbol 16

3.2 DM74126 Connection Diagram 17

3.3 HD7474 Connection Diagram 18

3.4 HD7408 Connection Diagram 18

3.5 EN7408 Connection Diagram 19

3.6 SRD-05VDC- SL-C Connection Diagram 20

4.1 White list program (WebGate Advanced Call Manager

v2.66)

21

4.2 Home Controller Block Diagram 22


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Figure No. Title Page No.

4.3 DTMF Detection unit construction with photograph

for the practical work

23

4.4 Device Status check section with photograph for the

practical work

24

4.5Tri-state buffer with LM555 monostable multi-

vibrator with photographs for the practical work25

4.67474 D flip-flop connection Diagram, with

photograph for it in the practical work26

4.7 Astable multi-vibrator with photograph for it in the

practical work27

4.8 The system case 27

4.9 The system board 28


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Abbreviations used

DTMF Dual-Tone Multi Frequency

ITU-T International Telecommunication Union – Telecommunication

Standardization Sector Recommendation

DFT Discrete Fourier Transform

FFT Fast Fourier Transform

BCD Binary Coded Decimal


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Abstract

In many cases it is desirable to turn on or off some appliances, such as air conditioning and

heating units before arriving home, this is known as home automation systems. This

project uses the Dual-Tone Multi Frequency (DTMF) technique used in touch tone

telephones, to control multi electronic devices from long distances using the mobile phone.

A practical application case for this system was implemented to control four electronic

devices. A test to detect the DTMF signal received from different mobile phones was also

carried out. The DTMF decoder was tested for accurate detection of the presence of these

tones under various conditions. The automation features of this work makes it possible for

homeowners to remotely control a large number of appliances, indoor and outdoor lamps

and lights, landscape sprinkler timers and more using their mobile phones.


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Introduction

The remote control used in home automation systems, is a wonderful feature that

everyone would like to enjoy, if they were not expensive to install, maintain, and able to be

used from long distance. The idea of the remotely controlled home automation systems is

shown in Figure 1.1.

Figure 1.1 Home Automation system

The home automation have many features makes the homeowner remotely toggle

appliances such as air conditioning and heating units, lamps or porch lights, landscape

sprinkler timers, snow-melt systems, outdoor property lighting, and safety lighting.

The mobile phones and Touch-Tone telephones use the Dual-Tone Multi Frequency

(DTMF). That was developed initially for telephony signaling such as dialing and

automatic redial. Each key-press on the phone keypad generates DTMF signal consists of

two tones that must be generated simultaneously.


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Chapter 1 Introduction

1.1 System Overview

Using the DTMF technology, the system in this project will control multi electronic

devices from long distance using the mobile phone.

This system allows the user to control and know the present state of home

appliances by cell phone, it can be done by send signal over the cell phone (control phone)

to other cell phone in the home (home-based phone), this cell phone is connected to an

interface circuit detects the DTMF signals and give it the access to a control unit which

controls the home devices and turn the power of these devices On or Off.

A design of a home appliances control system using cell phone presented in this

project is shown in Figure 1.2.

Figure 1.2 Appliances control using mobile phone

Home-based phone Control phone


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Chapter 1 Introduction

1.2 The System Features

This system can control up to 10 devices, it may be any electric or electronic

appliances, and each device is given a unique code.

There is no risk for false switching, it makes accurate switching any false switching

the device are not done.

This system doesn’t cost a lot of money, and it’s easy to implement.

Before changing the state of the device we can confirm the present status of the

device.

The system gives an acknowledgement tone after switching on the devices to

confirm the status of the devices.

Its highly secured system using the white list programs on the home-based phone to

block any other call from controlling the home appliances.

This system can be controlled by multi users, this feature refer to user choice.

1.3 The System Description

The Home Controller divided into two units which is, the DTMF detection unit, and the

device control unit, these units consists of many sub-circuit blocks, beginning with the

DTMF decoder, 4-16 line decoder/de-multiplexer, some D-flip-flops, relay driver circuits,

feedback circuitry, etc.


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Chapter 2


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DTMF Detection Unit

DTMF detection is the main object before starting to control the appliances. In this chapter

we will discuss in details the DTMF signaling and detection using several methods, and

later we will show the integrated circuit we use in this project, and how to get its output on

16 different output line.

2.1 DTMF Signaling

DTMF signaling, increasingly being employed worldwide with push-button telephone sets,

offers a high dialing speed over the dial-pulse signaling used in conventional rotary

telephone sets. In recent years, DTMF signaling also found many applications such as

automatic redial, modems that use DTMF for dialing stored numbers to connect with

network service providers. DTMF has also been used in interactive remote access control

with computerized automatic response systems such as airline’s information systems,

remote voice mailboxes, electronic banking systems, as well as many semiautomatic

services via telephone networks. DTMF signaling scheme, reception, testing, and

implementation requirements are defined in the International Telecommunication Union

Recommendations ITU-T Q.23 and Q.24.

DTMF generation is based on a 4×4 grid matrix shown in Figure 2.1. This matrix

represents 16 DTMF signals including numbers 0 – 9, special keys * and #, and four letters

A – D. The letters A – D are assigned to unique functions for special communication systems

such as the military telephony systems.

The DTMF signals are based on eight specific frequencies defined by two mutuallyexclusive groups. Each DTMF signal consists of two tones that must be generated

simultaneously. One is chosen from the low-frequency group to represent the row index,

and the other is chosen from the high-frequency group for the column index [3].

The implementation of a DTMF signal involves adding two finite-length digital

sinusoidal sequences with the later simply generated by using look-up tables or by

computing a polynomial expansion [2]. By pressing a key, for example number 3, it will


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Chapter 2 DTMF Detection Unit

generate a dual-tone consist of 697 Hz for the low group, and 1477 Hz for the high group,

as shown in Figure 2.2.

Figure 2.1 Telephone keypad matrix [3]

Figure 2.2 DTMF signal of key number ”3” [697,1477] Hz


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A DTMF decoder must able to accurately detect the presence of these tones

specified by ITU-T Q.23. The decoder must detect the DTMF signals under various

conditions such as frequency offsets, power level variations, DTMF reception timing

inconsistencies, etc. DTMF decoder implementation requirements are detailed in ITU-T

Q.24 recommendation.

For voice over IP (VoIP) applications, a challenge for DTMF signaling is to pass

through the VoIP networks via speech coders and decoders. When DTMF signaling is used

with VoIP networks, the DTMF signaling events can be sent in data packet types. The

procedure of how to carry the DTMF signaling and other telephony events in real-time

transport protocol (RTP) packet is defined by Internet engineering task force RFC2833specification [3].

2.2 DTMF Detection

This section introduces methods for detecting DTMF tones used in communication

networks. The correct detection of a DTMF digit requires both a valid tone pair and the

correct timing intervals. The DTMF signaling may be used to set up a call and to control

functions, for that it is necessary to detect DTMF signal in the presence of speech [3].

Since the signaling frequencies are all located in the frequency band used for

speech transmission, this is an in-band system. Interfacing with the analog input and output

devices is provided by codec (coder/decoder) chips, or A/D and D/A converters.

Although a number of chips with analog circuitry are available for the generation

and decoding of DTMF signals in a single channel, these functions can also be

implemented digitally on DSP chips [2].

2.2.1 DTMF Decoder Specifications

The implementation of DTMF decoder involves the detection of the DTMF tones, and

determination of the correct silence between the tones. In addition, it is necessary to

perform additional assessments to ensure that the decoder can accurately distinguish

DTMF signals in the presence of speech.


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For North America, DTMF decoders are required to detect frequencies with a

tolerance of ±1.5%. The frequencies that are offset by ±3.5% or greater must not be

recognized as DTMF signals. For Japan, the detection of frequencies has a tolerance of

±1.8 %, and the tone offset is limited to ±3.0 %. The ITU-T requirements for North

America are listed in the Table 2.1.

Another requirement is the ability to detect DTMF signals when two tones are

received at different levels. This level difference is called twist. The high-frequency tone

may be received at a lower level than the low-frequency tone due to the magnitude

response of the communication channel, and this situation is described as a forward (or

standard) twist. Reverse twist occurs when the received low-frequency tone has lower level

than the high-frequency tone.

The final requirement is that the receiver must avoid incorrectly identifying the

speech signal as valid DTMF tones. This is referred as talk-off performance [3].

Table 2.1 Requirements of DTMF specified in ITU-T Q.24

Signal frequencies Low group 697, 770, 852, 941 Hz

High group 1209, 1336, 1477, 1633 Hz

Frequency tolerance Operation ≤ 1.5%

Nonoperation ≥ 3.5%

Signal duration Operation 40 ms min

Nonoperation 23 ms max

Twist Forward 8 dB max

Reverse 4 dB max

Signal power Operation 0 to −25 dBm

Nonoperation −55 dBm max

Interference by echoes Echoes Should tolerate echoes delayed up to

20 ms and at least 10 dB down


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Bandpass

Filter 1#

Bandpass

Filter 2#

Bandpass

Filter 3#

Bandpass

Filter 4#

Bandpass

Filter 5#

Bandpass

Filter 6#

Bandpass

Filter 7#

Bandpass

Filter 8#

Lowpass Filter

Highpass Filter

Limiter

Limiter

697 Hz

770 Hz

852 Hz

941 Hz

1209 Hz

1336 Hz

1477 Hz

1336 Hz

Low group

tones

High group

tones

2.2.2 DTMF Detection Methods

The scheme used to identify the two frequencies associated with the button that has been

pressed is shown in Figure 2.3. Here, the two tones are first separated by a low pass and a

high pass filter. The passband cutoff frequency of the low pass filter is slightly above 100

Hz, whereas that of the high pass filter is slightly below 1200 Hz. The output of each filter

is next converted into a square wave by a limiter and then processed by a bank of bandpass

filters with narrow passbands. The four bandpass filters in the low-frequency channel have

center frequencies at 697 Hz, 770 Hz, 852 Hz, and 941 Hz. The four band pass filters in

the high-frequency channel have center frequencies at 1209 Hz, 1336 Hz, 1477 Hz, and

1633 Hz. The detector following each band pass filter develops the necessary dc switching

signal if its input voltage is above a certain threshold.

Figure 2.3 The DTMF detection secheme [2]


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The entire signal processing functions described above are usually implemented in

practice in the analog domain. However, increasingly, these functions are being

implemented using digital techniques.

Digital techniques surpass analog equivalents in performance, since it provides

better precision, stability, versatility, and reprogrammability to meet other tone standards.

The DTMF digital decoder computes the Discrete Fourier Transform (DFT) samples

closest in frequency to the eight DTMF fundamental tones. The DFT computation scheme

employed is a slightly modified version of Goretzel’s Algorithm. The flow chart of DTMF

detection using the modified Goertzel’s Algorithm is illustrated in Figure 2.4. Six tests are

followed to determine if a valid DTMF digit has been detected [2].

Magnitude test : According to ITU Q.24, the maximum signal level transmit to the public

network shall not exceed −9 dBm. This limits an average voice range of −35 dBm for a

very weak long-distance call to −10 dBm for a local call. A DTMF receiver is expected

to operate at an average range of −29 to +1 dBm. Thus, the largest magnitude in each

band must be greater than a threshold of −29 dBm; otherwise, the DTMF signal should

not be detected.

Twist test: The tones may be attenuated according to the telephone system’s gains at the

tonal frequencies. Therefore, we do not expect the received tones to have same

amplitude, even though they may be transmitted with the same strength. Twist is

defined as the difference, in decibels, between the low and high-frequency tone levels.

Frequency-offset test: This test prevents some broadband signals from being detected as

DTMF tones. If the effective DTMF tones are present, the power levels at those twofrequencies should be much higher than the power levels at the other frequencies. To

perform this test, the largest magnitude in each group is compared to the magnitudes of

other frequencies in that group. The difference must be greater than the predetermined

threshold in each group.

Total-energy test: Similar to the frequency-offset test, the goal of total-energy test is to

reject some broadband signals to further improve the robustness of a DTMF decoder.

To perform this test, three different constants c1, c2, and c3 are used. The energy of the


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Table 2.2 The respective DTMF data into BCD digits [4]

Flow Fhigh Key Q4 Q3 Q2 Q1

697 1209 1 0 0 0 1

697 1336 2 0 0 1 0

697 1477 3 0 0 1 1

770 1209 4 0 1 0 0

770 1336 5 0 1 0 1

770 1477 6 0 1 1 0

852 1209 7 0 1 1 1

852 1336 8 1 0 0 0

852 1477 9 1 0 0 1

941 1209 0 1 0 1 0

941 1336 * 1 0 1 1

941 1477 # 1 1 0 0

697 1633 A 1 1 0 1

770 1633 B 1 1 1 0

852 1633 C 1 1 1 1

941 1633 D 0 0 0 0

External component count is minimized by provision of an on-chip differential

input amplifier, clock generator, and latched tri-state interface bus. Minimal external

components required include a low-cost 3.579545 MHz crystal, a timing resistor, and a

timing capacitor. It can also inhibit the decoding of fourth column digits. The Block

Diagram of CM8870 shown in Figure 2.5 [4].

The CM8870’s internal architecture consists of a band split filter section which

separates the high and low tones of the received pair, followed by a digital decode

(counting) section which verifies both the frequency and duration of the received tones

before passing the resultant 4-bit code to the output bus.

The filter section also incorporates notches at 350 Hz and 440 Hz which provides

excellent dial tone rejection. Each filter output is followed by a single order switched

capacitor section which smoothes the signals prior to limiting. Signal limiting is performed

by high gain comparators [4].


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Figure 2.5 The Block Diagram of CM8870 [4]

The CM8870 decoder uses a digital counting technique to determine the

frequencies of the limited tones and to verify that these tones correspond to standard

DTMF frequencies. A complex averaging algorithm is used to protect against tone

simulation by extraneous signals (such as voice) while providing tolerance to small

frequency variations. The averaging algorithm has been developed to ensure an optimum

combination of immunity to “talk -off” and tolerance to the presence of interfering signals

and noise. When the detector recognizes the simultaneous presence of two valid tones

known as “signal condition”, it raises the Early Steering Flag (ESt) Any subsequent loss of

signal condition will cause ESt to fall.

Before the registration of a decoded tone pair, the receiver checks for a valid signalduration referred to as “character recognition-condition”. This check is performed by an

external RC time constant driven by ESt. Logic high on ESt causes the voltage on the

capacitor VC to rise as the capacitor discharges. Providing signal condition is maintained

(ESt remains high) for the validation period called Guard time period tGTP, VC reaches the

threshold voltage VTSt of the steering logic to register the tone pair, thus latching its

corresponding 4-bit code into the output latch.


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At this point, the GT output is activated and drives VC to VDD. GT continues to

drive high as long as ESt remains high, signaling that a received tone pair has been

registered. The contents of the output latch are made available on the 4-bit output bus by

raising the Three-State Control Input TOE to logic high. The steering circuit works in

reverse to validate the inter digit pause between signals. Thus, as well as rejecting signals

too short to be considered valid, the receiver will tolerate signal interruptions too short to

be considered a valid pause. This capability together with the capability of selecting the

steering time constants externally, allows the designer to tailor performance to meet a wide

variety of system requirements [4].

2.4 The Control Unit Interfacing

To have the BCD output on 16 different lines, we feed the DTMF decoder output to a 4-16

line decoder like IC74154. This IC takes the BCD number and decodes. According to that

BCD number it selects the active low output line from 1 to 16 which is decimal equivalent

of the BCD number present at its input pins. To get a logical high output, the output of the

IC74154 needs to get inverted. This inversion is carried out by an inverter, like the hex

inverter IC 7404. This IC inverts the data on its input terminal and gives inverted output.

The DM74154 integrated circuit is a 4-16 line decoder; it takes the 4 line BCD

input and selects respective output, one among the 16 output lines. It is active low output

IC so when any output line is selected it is indicated by an active low signal; the rest of the

output lines will remain active high, when both the strobe inputs, G1 and G2, are low. The

de-multiplexing function is performed by using the 4 input lines to address the output line,

passing data from one of the strobe inputs with the other strobe input low. When either

strobe input is high, all outputs are high. These de-multiplexers are ideally suited for

implementing high-performance memory decoders. All inputs are buffered and input

clamping diodes are provided to minimize transmission-line effects and thereby simplify

system design; the multiplexer/de-multiplexer diagram in Figure 2.6, and the truth table for

this de-multiplexer shown in Table 2.3 [4].


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Figure 2.6 Block diagram of the decoder chip 74154 [4]

Table 2.3 The DM74154 decoder truth table [4]

L – Logic low H – Logic High X – No change

G1 G2 D C B A 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

L L L L L L L H H H H H H H H H H H H H H H

L L L L L H H L H H H H H H H H H H H H H H

L L L L H L H H L H H H H H H H H H H H H H

L L L L H H H H H L H H H H H H H H H H H H

L L L H L L H H H H L H H H H H H H H H H H

L L L H L H H H H H H L H H H H H H H H H H

L L L H H L H H H H H H L H H H H H H H H H

L L L H H H H H H H H H H L H H H H H H H H

L L H L L L H H H H H H H H L H H H H H H H

L L H L L H H H H H H H H H H L H H H H H H

L L H L H L H H H H H H H H H H L H H H H H

L L H L H H H H H H H H H H H H H L H H H H

L L H H L L H H H H H H H H H H H H L H H H

L L H H L H H H H H H H H H H H H H H L H H

L L H H H L H H H H H H H H H H H H H H L H

L L H H H H L H H H H H H H H H H H H H H L

L H X X X X H H H H H H H H H H H H H H H H

H L X X X X H H H H H H H H H H H H H H H H

H H X X X X H H H H H H H H H H H H H H H H


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Chapter 3


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Control Unit

The Device Control unit designed for this project consists of device switching

section, device status feedback section, and relay driver circuit. In this chapter we will

show the main components of each section of this unit.

3.1 Device Switching Section

The main object of the device switching section, is giving access to the relay drive circuit

when needed to turn On/Off the controlled devices.

The Device Switching section consists of a tri-state buffer and flip-flops. The tri-

state buffer contains independent gates each of which performs a buffer function. The

outputs have the 3-STATE feature. When control signal is at high state, the outputs are

nothing but the data present at its input terminals. When control signal is at low state, the

outputs are held at high impedance state, so no output will be available at the output

terminal. Figure 3.1 illustrate the 3-state feature.

Figure 3.1 3 state buffer symbol

The tri-state buffer will lead the device control unit to operate in two different

ways. First for device status check before switching On/Off any device (the tri-state buffer

is disable), to avoid any confusion about the device present status of the output, this can be

done by fed the BCD decoder inverted output and the output line of the respective device

to the device status feedback section. The second way that the device control unit operates

Input

Output

Control signal


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Chapter 3 Control Unit

is after making confirmation of current status of the device to alter the status of that device,

now we have to enable the tri-state buffer by making the control input high. That make the

output of the tri state buffer be the signal at its input terminal. Now the device code of the

chosen relay whose status is to be altered is again pressed.

The DM74126 IC contains four independent gates each of which performs a non-

inverting buffer function. The outputs have the 3-STATE feature. When enabled, the

outputs exhibit the low impedance characteristics of a standard output with additional drive

capability to permit the driving of bus lines without external resistors, when disabled, both

the output transistors are turned OFF presenting a high-impedance state to the bus line.

Figure 3.2 show the connection diagram of this IC [4].

Figure 3.2 DM74126 Connection Diagram [4]

The output of the tri-state buffer is latched by using a D flip-flop. This D flip flop is

used in the toggle mode. For each positive going edge of the clock a pulse will trigger theflip flop.

The HD7474 is a dual positive edge-triggered D-type flip-flop. This IC consists of

two D flip-flops. These flip-flops are used to latch the data that present at its input

terminal. Each flip-flop has one data, one clock, one clear, and one preset input terminals.

Figure 3.3 show its connection diagram [4].


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Figure 3.3 HD7474 Connection Diagram [4]

3.2 Device Status Feedback Section

Before and after changing the present status of the device On/Off , it’s important to check

the status of the device. The control unit will give a feedback tone after switching On any

device, this help us to check the device status.

3.2.1 The Feedback Circuitry

This status feedback circuitry, utilizes a dual input AND gate, When the both inputs are

high that indicates that the device is switched ON, then the output of the AND gate goes

logic high state. This output is fed to the beep generator. When we press the key the

feedback tone is heard. This feedback tone is heard only when the device is switched ON.

After switching OFF the device, this tone is not heard.

The HD7408 contains four independent gates each of which performs the logic

AND function. The Connection diagram of this IC is shown in figure 3.4.

Figure 3.4 HD7408 Connection Diagram [4]


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3.2.2 Beep Tone Generator

The beep tone generator section produces a beep tone of audible frequency. This unit is

constructed using a 555 timer chip. Here it is wired as an astable multi-vibrator with a few

external components like resister and capacitor, required along with the timer 555 chip set.

This frequency comes in the audible range between 40 to 650 Hz. It should be less than

650 Hz otherwise it will mix up with the DTMF tone. The EN555 timer chip connection

diagram is shown in Figure 3.5.

Figure 3.5 EN7408 Connection Diagram [4]

We will discuss later the working of the timer 555 chip as an astable multi-vibrator.

3.3 Relay Drive Circuit

In order to switch the appliances On or Off, small board type relays were used. Since the

output of the D flip flop is normally +5 V or it is the voltage of logic high state, we cannot

use this output to run the device or appliances. Therefore here we use relays which can

handle a high voltage of 230 V or more, and a high current in the rate of 10 A to energize

the electromagnetic coil of the relays +5 V is sufficient.

Here we use four SRD-05VDC- SL-C relays to switch On/Off four different

devices. The connection diagram of this relay is shown in the Figure 3.6.


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Figure 3.6 SRD-05VDC- SL-C Connection Diagram

And to protect the relay coils from damage we use a single IN4007 diode,

connected in reverse between the coil terminals.

1


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Chapter 4


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Chapter 4 Overall System Design and Practical work

4.2 The System block diagram

Figure 4.2 Home Controller Block Diagram

-- DTMF Detection Unit

-- Control Unit

-- 1

st

Status Feedback Section-- 2nd Status Feedback Section


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4.3 The DTMF Detection unit

As discussed in Chapter 2, the DTMF detection unit constructs of DTMF decoder,

4-16 line Decoder/de-multiplexer, and inverter to invert the output of the 4-16 line

Decoder/de-multiplexer.

In this project we use the CM8870 DTMF decoder for allowed the system to

decode the DTMF signals sent by the user through home-based phone in to BCD digits,

these digital codes fed to the input of the 4-16 line decoder/de-multiplexer input which in

turns selects respective output, one among the 16 output lines, It is active low output IC so

its needs to get inverted to get a logical high output. This inversion is carried out by hex

inverter IC 7404.

The DTMF detection unit is connected as shown in Figure 4.3. The internal clock

circuit of the DTMF decoder is completed with the addition of a standard television color

burst crystal or ceramic resonator having a resonant frequency of 3.579545 MHz.

Figure 4.3 DTMF Detection unit construction with photograph for the practical work

Steering

circuit

OP-amplifier

input


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The TOE (Tri-State output enable) pin in the DTMF decoder is an active low input

used to disable/enable the output latch. We connect it to VDD in order to have the output

latch enabled at all times.

The INH pin Inhibits detection of tones represents keys A, B, C, and D, and giving

the PD pin Logic high powers down the device and inhibits the oscillator, for that these

two pins are connected to the ground. While the gain selector GS pin Gives access to

output of front-end differential amplifier (shown in Figure 2.5) for connection of feedback

resistor.

4.4 The Control Unit

The control unit consists of device status check section, device switching section, device

status feedback section, and relay driver circuit.

Before switching On/Off any device, to avoid any confusion about the device

present status of the output, we can check the status of any device by fed the BCD decoder

inverted output (the button that the user pressed) and the output line of the respective

device (from the relay circuit) to independent block of And gates, where the output of the

And gates is connected to the beep tone generator (B), that generates a beep if the

respective device in the ON state. Figure 4.4 show the device status check section.

Figure 4.4 Device Status check section with photograph for the practical work

In this project we use HD7408 IC which provides quadruple two input positive And Gates.

From the BCD decoder output

From the respective device relay


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After checking the device status, the tri-state buffer mode can be changed by

making the control input high. This is done by pressing the “0” key. When this key is

pressed the output of the 4-16 line decoder goes low. This gives a triggering pulse to themonostable multi-vibrator which is built around the LM555. This will keep the output high

for about 5 seconds. In this time interval the output of the tri state buffer will be the signal

at its input terminal. Now the device code of the chosen relay (1, 2, 3 or 4) whose status is

to be altered is again pressed. The output of the tri-state buffer is latched by using a D flip-

flop. After a period of 5 s the output of the LM555 monostable multi-vibrator goes low and

puts the tri state buffer in the high impedance state. Therefore to change the status of any

other device to be done we must press again “0” key to make the tri-state buffer act as

input–output state and the respective code of the device is pressed. Figure 4.5 show the

Tri-state buffer with the LM555 monostable multi-vibrator circuit.

Figure 4.5 Tri-state buffer with LM555 monostable multi-vibrator

with photographs for the practical work

From the BCD

decoder output

To the D Flip-Flops


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We use the timer LM555 for monostable operation; in this mode of operation, the

timer functions as a one-shot. The external capacitor is initially held discharged by a

transistor inside the timer. Upon application of a positive trigger pulse of less than 1/3

VCC to pin 2, the flip-flop is set which both releases the short circuit across the capacitor

and drives the output high. The voltage across the capacitor then increases exponentially

for a period of time = 1.1 R C (we make it 5 seconds), at the end of which time the voltage

equals 2/3 VCC. The comparator then resets the flip-flop which in turn discharges the

capacitor and drives the output to its low state. During the timing cycle when the output is

high, the further application of a trigger pulse will not affect the circuit so long as the

trigger input is returned low.

The output of the tri-state buffer is latched by using a D flip-flop. This D flip-flop

is used in the toggle mode. For each positive going edge of the clock a pulse will trigger

the flip flop. As shown in Figure 4.6, the output of the tri-state buffer is connected to the

clock input, and the inverted output connected to the D input, this will make the D flip-flop

invert its output each time a trigger pulse applied from the tri-state buffer. The main reason

to use the D flip-flop is to keep the status of the tri-state buffer output after it disabled.

Figure 4.6 7474 D flip-flop connection Diagram, with photograph for it in the practical

work


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The beep tone generator constructed using a 555 timer chip wired as an astable

multi-vibrator with a few external components, required along with the timer 555 chip set.

The connection of the astable multi-vibrator is shown in Figure 4.7.

Figure 4.7 Astable multi-vibrator with photograph for it in the practical work

4.5 The Practical Work

This system has been implemented practically as shown in the Figures 4.8, 4.9.

Figure 4.8 The system case

5v

speaker

And gates

block output


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Figure 4.9 The system board


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Chapter 5


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Conclusions and Future Work

5.1 Conclusions

During the realization of the presented project the following points can be depicted:

It is simple to control the operation of any where appliances by exploiting the

existing mobile network, i.e. it’s not necessary to install a specific network.

Any type of mobiles can do the job.

The control circuit is reliable and simple to build.

The system is secure, by black listing all the call number except that of the specific

users (installed in the white list).

The system can let the user know the status of the appliances, before and after the

switching.

The system is implemented practically and the expected results are obtained.

Some practical problems are encountered during the realization of the practical

implementation and are solved using the substitution component.

5.2 Future Work

In this system we did not use any applications on the control mobile, so for a future

work it will be useful to develop programs for the mobile devices to give more control

options and security control.

As a future work in the field of the presented project, we suggest to develop thesystem using PLCs or Microcontrollers instead of the control unit, to give more reliability

and control options, as temperature control, security and more computational work so the

system can do more than just turn On/Off the devices.


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References

[1] Fathia H. A. Salem, A Design of a Home Appliances Control System using Cell phone

& J2ME , A Thesis Submitted in Partial Fulfillment of the Requirement for the

Degree of Master of Science in Electrical and Electronic Engineering, University of

Garyounis, Benghazi-Libya, 2008.

[2] Sanjit K. Mitra, Digital Signal Processing , Second Edition, McGraw-Hill, University

of California, International Edition, 2002.

[3] Sen M Kuo, Bob H Lee, Wenshun Tian, Real-Time Digital Signal Processing

Implementations and Applications, Second Edition, John Wiley & Sons, Ltd, 2006.

[4] www.datasheetcatalog.com

[5] Gunter Schmer, DTMF Tone Generation and Detection: An Implementation Using theTMS320C54x, Application Report, Texas Instrument, May 2000


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Appendices


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Appendix A

ITU-T Q.24 Recommendations

MULTIFREQUENCY PUSH-BUTTON SIGNAL RECEPTION

1 Introduction

Characteristics of multi-frequency push-button (MFPB) telephone sets using voice frequency

signals are included in Recommendation Q.23. This Recommendation Q.24 is intended

primarily for application in local exchanges for the reception of MFPB signals. Other MFPB

signal receiving applications, such as transit exchanges, would need to take into account the

effects of transmission impairments, such as signal clipping, that could be introduced in long

distance telephone networks. Since technical factors, such as transmission loss, vary among

national networks, varying national standards exist.

Varying standards may also exist, for example, to incorporate differences between

local and transit exchange applications. This Recommendation is not intended to supersede

existing national standards nor is it intended to imply that Administrations should modify

those standards.

2 Technical parameters

2.1 General

The technical parameters identified herein are fundamental to the MFPB receiving

function and reasons are given for the importance of each parameter. The parameters require

operational values to be specified for compatibility with the MFPB sending equipment

(Recommendation Q.23) and the network environment in which the receiving equipment must

function. Annex A contains a Table showing values for some of these parameters that have been adopted by various Administrations and RPOAs. In addition to the fundamental

parameters covered by this Recommendation, Administrations should consider whether other

parameters need specification to account for operating conditions found in their networks.


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2.2 Signal frequencies

Each signal consists of two frequencies taken from two mutually exclusive frequency

groups (a high group and a low group) of four frequencies each, as specified in

Recommendation Q.23. These frequencies and their allocation to form the various digits and

symbols of the push-button signaling code are defined in Recommendation Q.23. The

exchange shall provide a check for the simultaneous presence of one and only one frequency

from the high group and one and only one from the low group.

2.3 Frequency tolerances

The exchange should respond to signals whose frequencies are within the tolerances

for MFPB sending. Somewhat wider tolerances may be appropriate, for example to cater for

transmission impairments encountered in subscriber cables or FDM transmission facilities.

However, wider limits may increase susceptibility to noise and digit simulation by speech.

2.4 Power levels

The exchange should provide proper reception of signals whose power levels are

determined by the amplitude of the sending equipment and loss that may be introduced by the

subscriber cables or other network elements. The sending amplitude and transmission

attenuation may be different for different frequencies. The reception characteristics may take

advantage of a limitation, if specified, on the maximum difference in power level between the

two received frequencies forming a valid signal to facilitate improved overall performance.

2.5 Signal reception timing

The exchange should recognize signals whose duration exceeds the minimum expected

value from subscribers. To guard against false signal indications the exchange should not

respond to signals whose duration is less than a specified maximum value. Similarly, pause

intervals greater than a specified minimum value should be recognized by the exchange. To

minimize erroneous double-registration of a signal if reception is interrupted by a short break

in transmission or by a noise pulse, interruptions shorter than a specified maximum value must

not be recognized. The maximum rate at which signals can be received (signaling velocity)


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may be related to the above minimum values. All of these values may also be determined by

subscriber feature requirements.

2.6 Signal simulation by speech

Because telephone set speech transmitters are normally connected in the circuit during

the push-button dialing interval, it is necessary for the exchange to properly receive valid

MFPB signals in the presence of voice or other disturbances. The nature of such disturbances

may vary from one geographical area to another. The number of calls affected by signal

simulation should not significantly degrade the overall telephone network performance

experienced by subscribers.

Since actual immunity to digit simulation may be difficult to measure, a test environment

using recorded speech, music, and other voice frequency sounds may be utilized to verify

design performance.

2.7 Interference by dial tone

MFPB reception should not be adversely affected while dial tone is being applied.

Characteristics of dial tone such as frequencies, power levels and spurious components are

covered in Recommendation Q.35. These characteristics are specified to minimize the

interference between the dial tone sending and the MFPB receiving functions. These functions

are normally provided by closely related exchange equipment which must be designed to

function properly over the entire range of signal characteristics and transmission impairments

to be encountered.

2.8 Interference by echos

MFPB signal reception from extended subscriber lines having long 4-wire

transmission sections must discriminate between a true signal condition and an echo condition

which may persist for a number of milliseconds. Failure to provide such discrimination could

result in signal reception errors, for example due to a reduction of the detected pause duration.


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Administrations having such extended subscriber lines with MFPB signalling should therefore

specify the echo conditions under which the MFPB signalling function must operate.

2.9 Noise immunity

Noise sources such as power lines, electric railways and telecommunication circuits

may induce electrical disturbances with various characteristics into MFPB signaling paths.

These disturbances may cause MFPB signals to be missed, split (double signal registration) or

cause signal simulation. The distortion products produced by the MFPB signaling source

should also be included in the noise environment. A realistic noise environment specification

and facilities for testing MFPB reception under the specified conditions, e.g., using recorded

test tapes, are important to ensure that performance standards will be met under actual service

conditions.


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Appendix B

Background: Goertzel Algorithm


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54/62


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© 2000 California Micro Devices Corp. All rights reserved.

9/28/2000

CM8870/70CALIFORNIA MICRO DEVICES

215 Topaz Street, Milpitas, California 95035 Tel: (408) 263-3214 Fax: (408) 263-7846 www.calmicro.com

CMOS Integrated DTMF Receiver

Features

Full DTMF receiver

• Less than 35mW power consumption

• Industrial temperature range

• Uses quartz crystal or ceramic resonators

• Adjustable acquisition and release times

• 18-pin DIP, 18-pin DIP EIAJ, 18-pin SOIC, 20-pinPLCC

• CM8870C

— Power down mode

— Inhibit mode

— Buffered OSC3 output (PLCC package only)

• CM8870C is fully compatible with CM8870 for 18-pindevices by grounding pins 5 and 6

Product Description

The CAMD CM8870/70C provides full DTMF receiver capability by integrating both the bandsplit filter and digital

decoder functions into a single 18-pin DIP, SOIC, or 20-pin PLCC package. The CM8870/70C is manufactured using

state-of-the-art CMOS process technology for low power consumption (35mW, max.) and precise data handling. The

filter section uses a switched capacitor technique for both high and low group filters and dial tone rejection. The

CM8870/70C decoder uses digital counting techniques for the detection and decoding of all 16 DTMF tone pairs into a

4-bit code. This DTMF receiver minimizes external component count by providing an on-chip differential input ampli-

fier, clock generator, and a latched three-state interface bus. The on-chip clock generator requires only a low cost TV

crystal or ceramic resonator as an external component.

Applications

• PABX

• Central office

• Mobile radio

• Remote control

• Remote data entry

• Call l imiting

• Telephone answering systems

• Paging systems


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©2000 California Micro Devices Corp. All rights reserved.

9/28/215 Topaz Street, Milpitas, California 95035 Tel: (408) 263-3214 Fax: (408) 263-7846 www.calmicro.com2

CALIFORNIA MICRO DEVICES CM8870/70

This device contains input protection

against damage due to high static

voltages or electric fields; however,

precautions should be taken to avoid

application of voltages higher than the

maximum rating.

Notes:

1. Exceeding these ratings may cause

permanent damage, functional

operation under these conditions is

not implied.

Absolute Maximum Ratings: (Note 1)

DC Characteristics: All voltages referenced to VSS

, VDD

= 5.0V ± 5%, TA = -40°C to +85°C unless otherwise noted.

Operating Characteristics: All voltages referenced to VSS

, VDD

= 5.0V ± 5%, TA = -40°C to +85°C unless otherwise noted.

Gain Setting Amplifier

SCITSIRETCARAHCCD

retemaraP lobmyS niM pyT xaM stinU snoitidnoCtseT

egatloVylppuSgnitarepO V DD 57.4 52.5 V

tnerruCylppuSgnitarepO I DD 0.3 0.7 Am

tnerruCylppuSybdnatS I QDD 52 µA V=DP DD

noitpmusnoCrewoP P O 51 53 Wm V;zHM975.3=f DD V0.5=

egatloVtupnIleveLwoL V LI 5.1 V V DD V0.5=

egatloVtupnIleveLhgiH V HI 5.3 V V DD V0.5=

tnerruCegak aeLtupnI I HI L / LI 1.0 µA V NI V= SS V= DD )1etoN(

EOTnotnerruC)ecruoS(pUlluP I os 5.6 02 µA V,V0=EOT DD V0.5=

)-NI,+NI(,ecnadepmItupnI R NI 8 01 MΩ zHK 1@

egatloVdlohserhTgnireetS V tsT 2.2 5.2 V V DD V0.5=

egatloVtuptuOleveLwoL V LO 30.0 V V DD daoLoN,V0.5=

egatloVtuptuOleveLhgiH V HO 79.4 V V DD daoLoN,V0.5=

tnerruC)k niS(woLtuptuO I LO

0.1 5.2 Am V TUO

V4.0=

tnerruC)ecruoS(hgiHtuptuO I HO 4.0 8.0 Am V TUO V6.4=

egatloVtuptuOV FER

V FER 4.2 7.2 V V DD daoLoN,V0.5=

ecnatsiseRtuptuO R RO 01 ΩΚ

SGNITARMUMIXAMETULOSBA

retemaraP lobmyS eulaV

V(egatloVylppuSrewoP DD -V SS )

V DD x aMV0.6

niPynanoegatloV cdV V SS VotV3.0- DD V3.0+

niPynanotnerruC I DD x aMAm01

erutarepmeTgnitarepO TA C°58+otC°04-

erutarepmeTegarotS TS C°051+otC°56-

SCITSIRETCARAHCGNITAREPO

retemaraP lobmyS niM pyT xaM stinU snoitidnoCtseT

tnerruCegak aeLtupnI I NI 001± An V SS V< NI V< DD

ecnatsiseRtupnI R NI 01 MΩ

egatloVtesffOtupnI V SO 52± Vm

noitce jeRylppuSrewoP RRSP 05 Bd )21etoN(zHK 1

noitce jeRedoMnommoC RRMC 04 Bd IV


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9/28/2000



AC Characteristics: All voltages referenced to VSS

, VDD

=5.0V ±5%, TA=-40°C to +85°C, f

CLK=3.579545 MHz using

test circuit (Fig. 1) unless otherwise noted.

Notes:1. dBm = decibels above or below a reference power

of 1 mW into a 600 ohm load.2. Digit sequence consists of all 16 DTMF tones.3. Tone duration = 40mS. Tone pause = 40 mS.4. Nominal DTMF frequencies are used.5. Both tones in the composite signal have

an equal amplitude.

6. Bandwidth limited (0 to 3 KHz) Gaussian Noise.7. The precise dial tone frequencies are

(350 Hz and 440 Hz) ±2%.8. For an error rate of better than 1 in 10,000

9. Referenced to lowest level frequency componentin DTMF signal.

10. Minimum signal acceptance level is measured withspecified maximum frequency deviation.

11. Input pins defined as IN+, IN-, and TOE.12. External voltage source used to bias VREF.

13. This parameter also applies to a third tone injected ontothe power supply.

14. Referenced to Figure 1. Input DTMF tone levelat -28 dBm.

SCITSIRETCARAHCCA

retemaraP lobmyS niM pyT xaM stinU setoN

sleveLlangiStupnIdilaV)langisetisopmocfoenothcae(

92- 1+ mBd 8,5,4,3,2,15.72 968 Vm SMR

tpeccAtsiwTevitisoP 01 Bd8,4,3,2

tpeccAtsiwTevitageN 01 Bd

timiLtpeccAnoitaiveD.qerF zH2±%5.1 .moN 01,8,5,3,2

timiLtce jeRnoitaiveD.qerF %5.3± .moN 5,3,2

ecnareloTenoTdrihT 61- Bd 41,31,9,8,5,4,3,2

ecnareloTesioN 21- Bd 9,8,6,5,4,3,2

ecnareloTenoTlaiD 22+ Bd 9,8,7,5,4,3,2

emiTnoitceteDtneserPenoT t PD 5 8 41 Sm otrefeRmargaiDgnimiTemiTnoitceteDtnesbAenoT t AD 5.0 3 5.8 Sm

tpeccAnoitaruDenoTniM t CER 04 Sm)elbatsu jdAresU(

eranwohssemiThtiwdeniatbo

)1.giFnitiucric

tce jeRnoitaruDenoTx aM t CER 02 Sm

tpeccAesuaPtigidretnI.niM t DI 04 Sm

tce jeResuaPtigidretnI.x aM t OD 02 µS

)QottS(yaleDnoitagaporP t QP 6 11 µS

V=EOT DD)DtSottS(yaleDnoitagaporP t SP tD 9 61 µS

)DtSotQ(pUteSataDtuptuO t SQ tD 4.3 µS

)QotEOT(yaleDnoitagaporPelbanE t

ETP 05 Sn

RL K 01= ΩCL Fp05=elbasiD t DTP 003 Sn

ycneuqerFk colC / latsyrC f K LC 9575.3 5975.3 1385.3 zHM

)2CSO(tuptuOk colC eviticapaCdaoL C OL 03 Fp


58/62




Explanation of Events

A) Tone bursts detected, tone duration invalid, outputs notupdated.

B) Tone #n detected, tone duration valid, tone decoded

and latched in outputs.C) End of tone #n detected, tone absent duration valid,

outputs remain latched until next valid tone.D) Outputs switched to high impedance state.

E) Tone #n + 1 detected, tone duration valid, tone decodedand latched in outputs (currently high impedance).

F) Acceptable dropout of tone #n + 1, tone absent duration

invalid, outputs remain latched.G) End of tone #n + 1 detected, tone absent duration valid,

outputs remain latched until next valid tone.

Explanation of Symbols

VIN DTMF composite input signal.

ESt Early Steering Output. Indicates detectionof valid tone frequencies.

St/GT Steering input/guard time output. Drivesexternal RC timing circuit.

Q1-Q4 4-bit decoded tone output.StD Delayed Steering Output. Indicates that

valid frequencies have been present/absent

for the required guard time, thus constitutinga valid signal.

TOE Tone Output Enable (input). A low levelshifts Q1-Q4 to its high impedance state.

tREC Maximum DTMF signal duration notdetected as valid.

tREC Minimum DTMF signal duration required

for valid recognition.tID Minimum time between valid DTMF signals.

tDO Maximum allowable drop-out during valid

DTMF signal.

tDP Time to detect the presence of validDTMF signals.tDA Time to detect the absence of valid

DTMF signals.tGTP Guard time, tone present.

tGTA Guard time, tone absent.


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9/28/2000



Functional Description

The CAMD CM8870/70C DTMF Integrated Receiver provides

the design engineer with not only low power consumption, but

high performance in a small 18-pin DIP, SOIC, or 20-pin PLCCpackage configuration. The CM8870/70C’s internal architec-

ture consists of a bandsplit filter section which separates the

high and low tones of the received pair, followed by a digitaldecode (counting) section which verifies both the frequency

and duration of the received tones before passing the result-ant 4-bit code to the output bus.

Filter Section

Separation of the low-group and high-group tones is achieved

by applying the dual-tone signal to the inputs of two 9 th-orderswitched capacitor bandpass filters. The bandwidths of these

filters correspond to the bands enclosing the low-group and

high-group tones (See Figure 3). The filter section alsoincorporates notches at 350 Hz and 440 Hz which provides

excellent dial tone rejection. Each filter output is followed by asingle order switched capacitor section which smooths the

signals prior to limiting. Signal limiting is performed by high-gain comparators. These comparators are provided with ahysteresis to prevent detection of unwanted low-level signals

and noise. The outputs of the comparators provide full-raillogic swings at the frequencies of the incoming tones.

Decoder Section

The CM8870/70C decoder uses a digital counting technique

to determine the frequencies of the limited tones and to verifythat these tones correspond to standard DTMF frequencies.

A complex averaging algorithm is used to protect against tone

simulation by extraneous signals (such as voice) whileproviding tolerance to small frequency variations. The

averaging algorithm has been developed to ensure an

optimum combination of immunity to “talk-off” and tolerance tothe presence of interfering signals (third tones) and noise.

When the detector recognizes the simultaneous presence oftwo valid tones (known as “signal condition”), it raises the

“Early Steering” flag (ESt). Any subsequent loss of signalcondition will cause ESt to fall.

Steering Circuit

Before the registration of a decoded tone pair, the receiver

checks for a valid signal duration (referred to as “character-

recognition-condition”). This check is performed by anexternal RC time constant driven by E

St. A logic high on ESt

causes VC (See Figure 4) to rise as the capacitor discharges.

Providing signal condition is maintained (ESt remains high) for

the validation period (tGTP), VC reaches the threshold (VTSt) ofthe steering logic to register the tone pair, thus latching itscorresponding 4-bit code (See Figure 2) into the output latch.

At this point, the GT output is activated and drives VC to VDD

.GT continues to drive high as long as ESt remains high,

signaling that a received tone pair has been registered. Thecontents of the output latch are made available on the 4-bit

output bus by raising the three-state control input (TOE) to a

logic high. The steering circuit works in reverse to validate theinterdigit pause between signals. Thus, as well as rejecting

signals too short to be considered valid, the receiver will

tolerate signal interruptions (drop outs) too short to be

considered a valid pause. This capability together with the

capability of selecting the steering time constants externally,

allows the designer to tailor performance to meet a widevariety of system requirements.

Guard Time AdjustmentIn situations which do not require independent selection of

receive and pause, the simple steering circuit of Figure 4 is

applicable. Component values are chosen according to thefollowing formula:

tREC

= tDP

+ tGTP

tGTP

» 0.67 RC

The value of tDP

is a parameter of the device and tREC

is the

minimum signal duration to be recognized by the receiver. Avalue for C of 0.1 uF is recommended for most applications,

leaving R to be selected by the designer. For example, asuitable value of R for a t

REC of 40 milliseconds would be 300K.

A typical circuit using this steering configuration is shown in

Figure 1. The timing requirements for most telecommunica-tion applications are satisfied with this circuit. Different

steering arrangements may be used to select independently

the guardtimes for tone-present (tGTP

) and tone absent (tGTA

).This may be necessary to meet system specifications which

place both accept and reject limits on both tone duration andinterdigit pause.

Guard time adjustment also allows the designer to tailor

system parameters such as talk-off and noise immunity.Increasing t

RECimproves talk-off performance, since it reduces

the probability that tones simulated by speech will maintain

signal condition for long enough to be registered. On theother hand, a relatively short t

REC with a long t

DO would be

appropriate for extremely noisy environments where fast

acquisition time and immunity to drop-outs would be require-ments. Design information for guard time adjustment is shown

in Figure 5.

Input Configuration

The input arrangement of the CM8870/70C provides a

differential input operational amplifier as well as a bias source(V

REF) which is used to bias the inputs at mid-rail.

Provision is made for connection of a feedback resistor to the

op-amp output (GS) for adjustment of gain.

In a single-ended configuration, the input pins are connectedas shown in Figure 1, with the op-amp connected for unity

gain and VREF biasing the input at ½ VDD

. Figure 6 shows the

differential configuration, which permits the adjustment of gainwith the feedback resistor R5.

Clock Circuit

The internal clock circuit is completed with the addition of a

standard television color burst crystal or ceramic resonatorhaving a resonant frequency of 3.579545 MHz. The

CM8870C in a PLCC package has a buffered oscillator output

(OSC3) that can be used to drive clock inputs of other devicessuch as a microprocessor or other CM887X’s as shown in

Figure 7. Multiple CM8870/70Cs can be connected as shownin figure 8 such that only one crystal or resonator is required.


60/62




Pin Function Table

Figure 1.

Single Ended Input Configuration

All resistors are ±±±±±1%tolerance.

All capacitors are ±±±±±5% tolerance.

F WOL F HGIH Y EK WOT Q4 Q3 Q2 Q1

796 9021 1 H 0 0 0 1

796 6331 2 H 0 0 1 0

796 7741 3 H 0 0 1 1

077 9021 4 H 0 1 0 0

077 6331 5 H 0 1 0 1

077 7741 6 H 0 1 1 0

258 9021 7 H 0 1 1 1

258 6331 8 H 1 0 0 0

258 7741 9 H 1 0 0 1

149 9021 0 H 1 0 1 0

149 6331 · H 1 0 1 1

149 7741 # H 1 1 0 0

796 3361 A H 1 1 0 1

077 3361 B H 1 1 1 0

258 3361 C H 1 1 1 1

149 3361 D H 0 0 0 0

- - Y NA L Z Z Z Z

ecnadepmIhgiH=Z,hgiHcigoL=H,woLcigol=L

NOITCNUFNIP

emaN noitpircseD

+NI tupnIgnitrevni-noNreifilpmalaitnereffiddne-tnorfehtotnoitcennoC

-NI tupnIgnitrevnI

SG tceleSniaG fonoitcennocrofreifilpmalaitnereffiddne-tnorffotuptuootsseccaseviG.rotsiserk cabdeef

V FER Vyllanimon(tuptuoegatlovecnerefeR DD .liar-dimtastupniehtsaibotdesuebyaM.)2 /

HNI Ddna,C,B,Asyek stneserpersenotfonoitcetedstibihnI

3CSO .tuptuorotallicsodereffublatigiD

DP nwoDrewoP .rotallicsoehtstibihnidnaecivedehtnwodsrewophgihcigoL

1CSO tupnIk colC.rotallicsolanretnisetelpmocsnipesehtneewtebdetcennoclatsyrczHM545975.3

2CSO tuptuOk colC

V SS .)VOotdetcennocyllamron(ylppusrewopevitageN

EOT QstuptuoehtselbanehgihcigoL.)tupni(elbanetuptuoetats-eerhT 1 Q- 4 .pu-lluplanretnI.

Q1

Q2Q3Q4

riapenotdilavtsalehtotgnidnopserrocedocehtsedivorp,EOTybdelbanenehW.stuptuoetats-eerhT.)2.giFeeS(.deviecer

DtS tuptuoehtdnaderetsigerneebsahriapenotdevieceranehwhgihcigolastneserP.tuptuognireetsdeyaleD

VwolebsllafTG / tSnoegatlovehtnehwwolcigolotsnruteR.detadpusihctal tST .

tSE elbazingocerastcetedmhtiroglalatigidehtnehwyletaidemmihgihcigolastneserP.tuptuognireetsylraE

.wolcigolaotnruterottSEesuaclliwnoitidnoclangisfossolyratnemomynA.)noitidnoclangis(riapenot

tG / tSVnahtretaergegatlovA.)lanoitceridib(tuptuoemitdraug / tupnignireetS tST ehtsesuactSadetceted

stidna,tnatsnocemitgnireetslanretx eehtteserotstcatuptuoTGehT.riapenotdetcetedehtretsigerotecived)2.giFeeS(.tSnoegatlovehtdnatSEfonoitcnufasietats

V DD .ylppusrewopevitisoP

CI .noitcennoClanretnI VotdeitebtsuM SS )ylnonoitarugifnoc0788rof(


61/62


9/28/2000



Figure 3. Typical Filter Characteristic Figure 4. Basic Steering Circuit

Figure 5. Guard Time Adjustment Figure 6. Differential Input Configuration


62/62


1

2

3

4

5

6

7

8

9

1

2

3

4

5

6

7

8

9

V

St/GT

ESt

StD

Q4

Q3

Q2

Q1

TOE

DD

ESt

StD

NC

Q4

Q3

Est

StD

NC

Q4

Q3

N C

I N +

I N -

V S t / G T

D D

G S

I N +

I N -

V S t / G T

D D

4

5

6

7

8

4

5

6

7

8

9 1 0

1 1

1 2

1 3

9 1 0

1 1

1 2

1 3

V

St/GT

ESt

StD

Q4

Q3

Q2

Q1

TOE

DD 18

17

16

15

14

13

12

11

10

18

17

16

15

14

13

12

11

10

IN+

IN-

GS

V

IC

IC

OSC1

OSC2

V

REF

SS

GS

V

IC

IC

OSC1

REF

V

INH

PD

OSC3

OSC1

REF18

17

16

15

14

18

17

16

15

14

3 2 1 2 0

1 9 3 2 1

2 0

1 9

O S C 2

V T O E

Q 1

Q 2

S S

O S C 2

V T O E

Q 1

Q 2

S S

IN+

IN-

GS

V

INH

IC

OSC1

OSC2

V

REF

SS

Ordering Information

Product Identification Number

PackageP — Plastic DIP (18)

F — Plastic SOP EIAJ (18)PE — PLCC (20)S — SOIC (18)

CM8870C

Pin Assignments

Example:

Figure 8. CM8870/70C Crystal ConnectionFigure 7. CM8870C Crystal Connection(PLCC Package Only)

CM8870

30pF

OSC1 OSC2 OSC3

OSC1 of other CM887X’s

Clock input of other devices

OSC1

3.58 Mhz 30pF 30pF

OSC1 OSC1OSC2 OSC2 OSC2

P — Plastic DIP (18)

F — Plastic SOP

EIAJ (18)

S — SOIC (18)

P — Plastic DIP (18)

F — Plastic SOP

EIAJ (18)

S — SOIC (18)

PE — PLCC (20)

* — Connect To VSS

PE — PLCC (20)

C M 8 8 7 0

C M 8 8 7 0

C

CM8870 CM8870C

I N -

I N +

I N -

I N +

*

*

* *

*

IP

appliansasasces control using mobile phone

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