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Contents
Acknowledgment
PCB Design and Remote Controller
Digital playback/record Unit
Project Goals
Illustration of Life-Saver
Project Objectives
Cost
reliability
Safety
Appearance
Ease of use
Responsibilities
Structure of Life-Saver
UHF remote controller
Illustration of UHF Remote Controller
Overview of traditional PCB design
PCB Design of UHF remote-controller
Signal conductors
Receiver circuit
Spacing
Supply and Ground Conductors
Automated Artwork Draughting
Procedure
Block Diagram
Layout sketch
Digitizing
Input Data
Photo Plotting
PCB Fabrication Process
Circuit Operation
PT2262 Encoding Section
PT 2272 Decoding Section
Transmitting Section
Receiving Section
Calibration Procedure
Transmitter
Receiver
Coding
Testing Report Document
Specification of UHF Remote Controller
Bill of Material and the raw material cost (estimated)
Auto dialer
Testing Report Document
Specification of Auto Dialer
Bill of Material and the raw material cost (estimated)
Users Manual
Digital playback/record unit
Illustration of Digital playback/record unit
Operation Principal
Schematic Circuit Diagram
Printed Circuit Board
PCB Layout
PCB Specification
Circuit Operation
Playback looping
Message Recording/normal Playback
ISD 1416 ChipCorder® technology
Testing Procedures
Users Manual
Recording message
Message Playback
Testing Report Document
Specification of Digital Recorder
Service Manual
Bill of Material and the raw material cost (estimated)
Design episode
Life-Saver Specification
Discussion
PCB Design and UHF Remote Controller
Auto Dialer
Digital playback/record Unit
Conclusion
Reference Books/Web Sites
This report also available on Internet

PCB Design and Remote Controller

We would like to give our most earnest thanks to our project supervisor Dr. Lau and Mr. Poon for their much needed, much appreciated, and invaluable guidance and assistance throughout the project.

We would also like to thank Mr. Thomas Lai, Senior Sales Engineer, Angus Electronics Co. Ltd. who sold the core logic IC PT-2262 and PT-2272 in a very small quantity, this initially enable us to commence this part of Life-Saver project.

Digital playback/record Unit

It is a pleasure to acknowledge the help of our project supervisor Dr. Lau and our friend Mr. Sheldon and Mr. John Chan whom have given us continued encouragement and every possible form of assistance throughout the entire period of preparation of this section of project. And Mr. Benny Wong who advise us to change from the phase-out 1016/1020 models to current product, the 1416/1420 series.

We would also like to acknowledge the people whose participation made the project possible:

Mr. Benny Wong

Sales Engineer

Marubun Hong Kong Ltd.

mrbhk@hkisl.net

Ms. Bonnie

Sales Manager

ParcShine Electronics Ltd.

parcshin@hkstar.com

Mr. David DiGiacomo

dd@Adobe.COM

Mr. Jaap van Ganswijk

ganswijk@xs4all.nl

Mr. John Chan

Manager

ComLogic Technology Co.

mlc@glink.net.hk

Mr. Sheldon

tadedek@flash.net

Mr. YK Chan

Sales Executive

ParcShine Electronics Ltd.

parcshin@hkstar.com

830,000 elderly persons whom age 65 or above living in Hong Kong. Many of them, say thousands are living alone in public rental or private house.

Although, the government would increase the total number to 126 teams of professional staffs enabling them to reach out about 12,000 elderly people living alone within the year. There are some unexpected situation may occur for those elder who living alone, such as cold spell in 1995, approximate 30 senior citizen were gone because the temperature suddenly crashed. For example, in the recent cold spell, government has focused attention on the issue of outreaching to elderly persons living alone. In emergency situations like this, the Social Welfare Department mobilizes a large number of professional staff to reach out, but the large number is 63 teams that only enabling them to reach out around 6,000 elder. It quite insufficient compared several thousand elder living alone in Hong Kong.

In addition to temperature changing, there are many housing incident such as fire, scald and some severe disease such as cardiac, etc. are grave peril to the elder living alone. Time is life! The faster rescue the more living chance! So, we would like to develop an automatic alarm system, called Life-Saver.

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Illustration of Life-Saver:

So far as we know, the housing authority currently used a simply alarm system, a wired system, the brief block diagram as follows,

d:\project\flow chart\fchart00.cfl

Compared with our system:

It quite insufficient in emergency used:

1. One must press button at a specific location. (less flexibility)
2. People seeing and/or hearing alarm and then call the appropriate party(ies). (waste valuable time)

The Life-Saver carried out the dramatic function over the traditional one:

1. wireless remote control. (great flexibility)
2. pocket size (remote control part) 55(W)*80(L)*15(H) (mm)
3. light weight (remote control part) 15gm (including battery)
4. one-touch triggering. Once button depressed, Life-Saver would automatically dial to inform the appropriate party(ies), such as relatives, friends or even though the 999.
5. a preset voice message will automatic looping when connection established.
6. up to 16 second message can be recorded.

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Life-Saver consists of three major parts, the UHF part, the telecommunication part and the electronics recording part. So, we have the opportunity to practice the knowledge we studied within the two years, such as how to design a ultra high speed PCB described in EDA subject, how to use Op-amp and the filter design described in Network and Circuit Analysis, some special filter - anti-aliasing filter described in embedded system and micro-controller and how to use testing equipment described in Instrumentation. By construct the Life-Saver, we are deeply understood the theory and we studied an ultimate important thing, how to apply the knowledge we got to the actual world.

On the other hand, in the modern business society, every produce would face the competitive, how to inexpensive to produce, reliable, safe and easy to use are four major part that affect the market shared of the product.

Cost

By using non-critical readily available hardware and electronic components.

reliability

By using solid-state active components and PCB construction techniques, a high degree of reliability will be obtained.

Safety

By using both battery for remote control and an fused power supply, insulated o/p terminals, and a completely plastic enclosure, safe operation will be assured.

Appearance

In order to down the cost, the plastic enclosure, either simply painted or covered with contact paper, will ensure relative attractive but low cost.

Ease of use

One-touch triggering with the use of a micro switch on the remote controller, a front panel-mounted LED indicator to acknowledge the signal received to ensure Life-Saver would had a high degree of functionality and be easy to use.

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Life-Saver consists of three major parts:

1. UHF remote controller
2. Auto dialer
3. Digital playback/record unit

UHF remote controller

Illustration of UHF Remote Controller

Overview of traditional PCB design

For PCB design, the first rule is to prepare each and every PCB layout as viewed from the component side (top side). This rule must be strictly followed to avoid confusion which would otherwise be caused.

Another important rile is not start the designing of a layout unless an absolutely clear circuit diagram is available, if necessary, with a component list.

Certain designers prefer to complete the component layout first and then start with the interconnections. Others develop the layout of components and interconnections simultaneously. But the common features of any approach should be to develop the layout in the direction of the flow as possible. Only this way will one achieve the shortest possible interconnections.

Among the components, the larger ones are placed first and the space in between is filled with smaller ones. Components requiring input/output connections come near the connectors.

In the designing of a PCB layout, it is very important to divide the circuit into functional sub-units. Each of these sub-units should be realized on a defined portion of the boars. So, we separated the remote controller into three different part - transmitter/encoder, receiver and decoder. This will prove helpful not only in functional reliability but also enables a faster testing and servicing of the board.

PCB Design of UHF remote-controller

Signal conductors

Signal conductors in our remote controller PCB's have to fulfill a variety of different tasks, (e.g., antenna, input, output, etc.) which minimizing the conductor length is the most important.

The length of any signal conductor should be made as short as possible. This is because the magnitude of the undesired inductive and capacitive coupling effects increases more or less proportionally to the length of the particular conductor.

The requirement to keep all signal conductors short, looks somewhat difficult to achieve. But a good approach is to have the most critical signal conductors identified and to put them first in the layout while the remaining ones are placed subsequently. This of course is only possible if the sensitive components have been placed accordingly.

(Appendix A-1) is initially PCB design circuit. The signal conductors is made to long and the traces is 90 degrees direction, so the signal include noise and unwanted signal.

(Appendix A-2) is final PCB design. The signal conductors is made to short and the traces should be given to the 45 degrees direction or 30/60 degrees direction. The result is better than the initially PCB design.

Receiver circuit

An improper layout of a high-frequency amplifier can also result in a reduced bandwidth of the amplifier. (Refer to Figure A-1) Shows such a situation. If the input and output conductors are close to each other, there can be a feedback resulting in oscillations. Also, if ground conductors are close to the signal conductors, the higher capacitance can reduce the bandwidth of the amplifier because this capacitance along with the output resistance acts a low-pass filter. The proximity of input and output conductors can further result in another interesting effect which is called Miller effect: The capacitance in between gets effectively multiplied by the amplifier gain and makes it to appear at the amplifier input thus further degrading the bandwidth. Herewith, sufficient spacing must be provided between such conductors to avoid this effect.

Spacing

(Appendix A-2) is to minimize the possible flash-over caused by over-voltage or contamination on the PCB surface. Such faults may occur inspite of maintaining conductor spacing within specified safety requirements. Sharply localized high-voltage gradients, found near low-angle conductor corners must be strictly avoided (Refer to Figure A-2). Minimum spacing specifications have to be interpreted as guidelines for cases where minimum spacing cannot be avoided. In all other cases, a sufficient margin has to be applied.

Not Recommended solution

recommended

(Appendix A-1) have FLASH OVER.

(Appendix A-2) is decreased the FLASH OVER.

Supply and Ground Conductors

When the supply and ground lines have to be put into the layout, they are not just conductive links. The width of such and the pattern in which they are distributed, is of highest importance for stability of the circuit voltage: If the potential reference system is unstable, then what other voltage.

The fundamental rule for any circuit is:

= conductor width of ground line

= conductor width of supply line

= conductor width of signal lines

(Refer to Figure A-3 and Appendix A-2.b) shows the configuration in single-and double-sided PCBs which must be aimed at. It is very clear that these configurations cannot be maintained throughout a layout, especially for signal-sided PCBs. In designing a good layout, care should be taken to see that they are implemented to the maximum extent possible.

Automated Artwork Draughting

There is a significant shortening of the turn-around time in PCB design. (Refer to Figure A-4).

Procedure

Block Diagram

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Layout sketch

(Appendix A-2) is using 'Puppets' for the circuit layout and is used in general for the concept of individually die-cut, transparent layout patterns that represent commonly used electronic components.

The use of 'puppets' help to save time in layout designing: It minimizes the time spent in erasing of components located and their redrawing plus redrawing of all the effected interconnections. The use of 'puppets' is recommended particularly where larger and more complicated layout are designed. It can help to save 20-50% of the layout designing time.

Digitizing

Using CAD of layout (OrCad, Protel, PCAD, etc.). The component placing and interconnecting patterns are developed with the assistance of computer facilities.

Input Data

Figure A-7 Component List

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Photo Plotting

In the photo plotter, the input data are converted back to graphics by photographic (Refer to Appendix A-7 to A-9).

PCB Fabrication Process

Step 1

Clean the blank PCB. The first step is probably the most important.

Step 2

Apply the Photoresist. While liquid photoresist can be applied by spraying, dipping, speed whirling, and roller coating, these methods are used primarily for mass-production in industry.

When the liquid photoresist is first applied, it really is not yet a resist, but a sensitizer. To take on the properties of a resist that will protect copper underneath, it must be dried and exposed to ultraviolet light.

Step 3

Dry the Photoresist and leave the board in a dark cabinet overnight to let it dry.

Step 4

Expose the Sensitized PCB to Ultraviolet Light. If the board were now placed under an ultraviolet light, the entire sensitized surface would turn to a resist, and no copper could be etched away.

Using an ultra-violet black light, set the printing frame so that it is directly facing the light, approximately 1 foot away. Be sure the surface is exposed to ultraviolet light and that the lamp holder does not cast shadows. Expose for a minimum of 2 minutes. When the exposure is complete, remote the PCB from the frame. The sensitized areas exposed to ultra-violet light are now hard and have formed into a resist.

Step 5

Develop the Image (Pattern). The purpose of the developing step is to remove the unwanted remaining sensitized material (where there was no ultraviolet exposure) and bring out the latent image of the traces and pads. While still under safe-light condition, place the board in a tray filled to a depth of ½ inch with developer. Cover the tray to avoid breathing harmful fumes, and rock the tray gently for about 20 minutes. Then, remove the board and let it drain. At this time return to normal lighting conditions. An image of the traces and pads should now be standing out in clear relief from the surrounding copper.

Steps 6

Rinse and Dry. Under cool, slow running water, rinse the board for 2 t0 3 minutes. Do not let the water hit the board directly, since it could smear the resist pattern.

Step 7

Of all the processes involved in making a PCB, the etching procedure is probably the easiest. Fill the etching container with acid to a depth that will cover the submerged PCB. Ideally, the board should be standing on edge. But if it must lie horizontally, be sure the copper side is facing up. Don't plunge the board into the acid; place it in the container.

Step 8

Using water to cleaning the Acid.

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Circuit Operation

PT2262 Encoding Section

PT2262 is a remote control encoder paired with PT2272 CMOS technology. It encodes data and address pins into a serial coded waveform suitable for RF or IR modulation. PT 2262 has a maximum of 12 bits of tri-state address pins providing up to 531,441 address codes; thereby drastically reducing any code collision and unauthorized code scanning possibilities.

PT2262 encode the code address and data set at A0 ~ A5 and A6/D5 ~ A11/D0 into a special waveform and output is to the DOUT when TE is pulled to "0" (low state). This waveform is fed to either the RF modulator or the IR transmitter for transmission. The transmitted radio frequency or infrared ray is received by the RF demodulator or IR receiver and reshaped to the special waveform. PT 2272 is then used to decode the waveform and set the corresponding output pin(s). Thus completing a remote control encoding and deciding function.

The build-in oscillator circuitry of PT 2262 allows a precision oscillator to be constructed by connecting an external resister between OSC1 and OSC2 pins. For PT 2272 to decode correctly the received waveform, the oscillator frequency of PT 2272 must be 2.5 ~ 8 times that of transmitting PT 2262.

An address/data bit can be designated as bit "0", "1" , or "f" if it is in low, high or floating state respectively . One bit waveform consists of 2 pulse cycle has 16 oscillating time periods. For further details, refer to diagram below:

PT 2272 Decoding Section

PT 2272 is a remote control decoder paired with PT 2262 utilizing CMOS technology. It has a maximum of 12 bits of tri-state address pins providing up to 531,441 address codes; thereby drastically reducing any code collision and unauthorized code scanning possibilities. PT 2272 is available in several options to suit every application needs: variable number of data output pins, latch or momentary output type.

PT 2272 decodes the waveform received and fed into the DIN pin. The waveform is decoded into code word that contains the address, data and sync bits. The decoded address bits are compared with the address set at the address input pins. If both addresses match for 2 consecutive code words, PT 2272 drives:

1. The data output pin(s) whose corresponding data bit(s) is then decoded to be a "1" bit, and
2. The VT output to high voltage (high state).

The build-in oscillator circuitry of PT 22272 allows a Precision oscillator to be constructed with only an external resistor. For the PT 2272 to decode correctly the waveform that was received, the oscillator frequency of PT 2272 must be 2.5 ~ 8 times that of the transmitting PT 2262.

An address/data bit can be designed as bit "0", "1" or "f" if it is in low, high or floating state respectively. One bit waveform consists of 2 pulse cycles. Each pulse has 16 oscillating time periods. For further details, refer to the diagram below:

Transmitting Section

By used the PT 2262, our transmitter circuit is very simple.

For our circuit need a CALL and a RESET button, so we connect two switch connected with A11, A10 and VT , as TE is a active low signal, so we used a diode to make sure a low signal is input.

When we press the CALL button, it will give a signal to A10 and TE. After encode and mixed with OSC signal. An encoded signal will pass to MSP10(a NPN type High frequency transistor) and LC circuit which given a high frequency for transmission.

f = 1/2LC = 1/(6.28*10mH*3.87nF) = 411.25MHz.

Receiving Section

At the first stage of our receiver, we used a turned LC circuit to catch the transmission signal. And pass the MSP10 as a RF amplifier. Then pass a bandpass -active filter which is usedMC4558(a two stage OAMP).

The center frequency f0 = 1/2RC Hz = 26.5 Hz.

At the center frequency the feedback loop passes no current and no attenuation occurs.

Then the second stage of MC4558 is used to amplified the input signal to PT 2272 DIN pin. After decode and PT 2272 will provided a signal to 4013 (a flip flop) which consider by the input signal. If we press the CALL ,button of the transmitter, then the PT 2272 will provide a output from A11 to pin D of 4013 and used 90132 to drive a relay circuit to trigger the auto dialer and digital recorder.

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Calibration Procedure

Transmitter

1. Set the SW3 and SW4 (DIP switch). Two switches must be match.
2. Connect Hi-frequency counter to point 1 (Refer to Appendix A-10). Adjust VC1 and press SW1 until the frequency is match the receiver.

Receiver

1. Connect the Hi-frequency counter to point 2 (Refer to Appendix A-11). Adjust VC2 and press SW1 until point 1 and point 2 are match.
2. Connect instrument to each stage (Refer to Appendix A-11). A sweep generator and marker signal is injected at the input of the stage, and an oscilloscope is connected at the input of the Op-Amp 4558 stage to check the frequency response.
3. Set the function generator to sine-wave 100kHZ and 1mV. At the point 3 (Refer to Appendix A-11) will measure a about 5V Peak-to-Peak sine-wave.

Coding

1. Install the receiver on the decoder board.
2. When press SW1(transmitter), the LED1 is ON until not press and LED2(receiver) is ON.
3. When press SW2(transmitter), the LED2(receiver) is OFF.

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Testing Report Document

See appendix A-0

Specification of UHF Remote Controller

Bill of Material and the raw material cost (estimated)

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Auto dialer

The auto dialer circuits consists of two ICs.

1. TP5700A

Telephone Speech Circuit

- It can be directly interfacing to a low voltage DTMF generator, Figure C-3 is shown.

- It can reduce the number of components required to build a pulse dialing telephone,

as shown in Figure C-4.

Figure C-2 Simplified Block Diagram

Figure C-2 Connection Diagram

Features :

2. MC145416

Tone/Pulse Dialer with

10 Number Memory

Plus 3 Emergency Numbers

Low-Power, Silicon-Gate CMOS

Figure C-5 MC145416 Pin assignment Diagram

Features :

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1. Actual Components

Motorola manufactures a series of combination dialing circuits; the MC145412, MC145413, MC145416, and MC145512. Figure C-6 is a block diagram for the MC145412/12/16/512 family. Each dialer interfaces directly with either 3 X 4 or 4 X 4 or 5 X 4 keypads. A single input pin will select between DTMF, 10 pps, or 20 pps dialing. An internal memory can hold up to 10 complete telephone numbers, each up to 18 digits long - this includes last number redial. Finally, the dialers operate on line power as low as 1.7 volts.

Figure C-6. Combined Dialer Block Diagrm. (Courtesy Motorola, Inc.)

Figure C-7 demonstrates an actual application of the MC145416. A standard 5 X 4 keypad is used to select desired digits. Keypad signals are connected to row and column inputs. A ground condition at the off-hook input will enable the dialer. While on-hook, numbers may be entered into memory without dialing signals being generated. A 3.58 MHz color burst crystal provides a stable time base for operation. Figure C-8 is shown a timing diagram.

Figure C-7. Combined Dialer Application

Figure C-8. Timing diagram

Dialing mode select can be logic high for 20 pps, open for 10 pps, or ground for DTMF signaling. DTMF tones are output to the DTMF OUT pin when the dialer is in the tone mode, and the pulse output (OPL) will be at high-impedance. In pulse dialing mode, the DTMF OUT pin is at high-impedance while pulses are delivered to the OPL pin. Mute is connected directly to the speech network. It will be logic low during pulsing or tone output, otherwise it will be logic high.

Make/break ratios are not field adjustable in the MC145416. Devices are mask programmed at the factory. Both the MC145416. Devices are mask programmed at the factory. Both the MC145412/13/16 offer a typical make/break ratio of 40/60. The MC145512 has a make/break ratio of 32/68.

Memory access and last number redial are accomplished easily by the integrated dialing circuits. For last number redial, the "*" and "0" buttons must be pressed. To retrieve a stored number, "*" and the corresponding number (1 through 9) must be pressed. A complete explanation of dialing key sequences is available in the MC145416 datasheet, Appendix C.

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2. A complete integrated auto dialer circuit

Integrated circuit tone/pulse dialing and speech circuit functions can be combined to form a complete, solid-state telephone which can provide such features as tone or pulse dialing with memory and redial, and an active speech network free of bulky transformers or coils. Figure C-9 is the complete schematic for a auto dialer circuit.

Figure C-9 A complete auto dialer circuit, refer to appendix C.

Testing Report Document

See appendix C-0

Specification of Auto Dialer

Bill of Material and the raw material cost (estimated)

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3. Sidetone Circuit and Adjustment

That portion of the talkers voice which is fed back to his/her receiver.

For the hybrid used in the central office exchange, the balancing network is adjusted so that no transmit signal appears at the receive terminals and no receive signal appears at the transmit terminals. However, for the induction coil arrangement in the auto dialer set, the balancing network is internationally unbalanced slightly so that a small amount of the transmitted signal is also fed to the receiver of the talking phone. This signal is called the sidetone.

Sidetone is necessary so that the person can hear his/her own voice from the receiver to determine how loudly to speak. The sidetone must be at the proper level because too much sidetone will cause the person to speak too softly for good reception by the called party. Conversely, too little sidetone will cause the person to speak so loudly that it may sound like a yell at the other end. In the circuit shown in Figure C-10, the values chosen for two resistance and a capacitance produce the proper level sidetone for most conditions .

Figure C-10 sidetone circuit

The level of sidetone cancellation may be adjusted by connecting an external balance impedance to SIDETONE (pin 4) and coupling this point to V+. For good sidetone cancellation the balance impedance should be approximately 10 times the subscriber line input impedance. Some typical component values to match a precise 600 ohm termination for test purposes are shown in Figure C-11(refer to appendix C).

The component values used for Z_BAL should be selected to provide a clear sidetone sound without excessive "hollowness". The capacitor value and ratio of the two resistors will fix the pole location. To avoid reducing the low voltage performance of the circuit the sum of the two resistors should not exceed 10 KW.

4. DTMF Dialing Using Integrated Circuits

To generate DTMF tones electronically, keypad closures are digitally converted into combinations of low and high frequency sine waves, which are mixed in pairs and amplified, to drive the speech network.

Dialing also may be accomplished by sending dual tones onto the line as discussed for the conventional phone. Integrated circuits have been designed to provide this function. The conventional way of accomplishing this is shown in Figure C-12a. Unlike the conventional way, in which a low-frequency and high-frequency sine wave oscillator feed the speech network, the integrated circuit DTMF generator (Figure C-12b) has a counter and decoder that counts pules from a crystal-controlled oscillator and provides output codes that correspond to the low-frequency tone required and the high-frequency tone required. Each of the two outputs from the counter feed into its own digital-to-analog (D/A) converter. the D/A converter, as the name implies, converts the digital code out of the counter to a sine-wave tone.

Figure C-12. DTMF Generators

4.2 Operational information

Activation of the tone output circuits in the integrated circuit DTMF generator begins with the caller pressing a key on the keypad. The keypad contacts may be arranged as shown in Figure C-13a. The top schematic is a representation of a standard DTMF keypad (like a double-pole single-throw switch) where a separate set of two contacts give the row and the column of the key being pushed. An alternative and somewhat less expensive arrangement is shown in the bottom schematic which is a so-called Class-A or single-pole single-throw configuration, with only one set of contacts for each row-column intersection. Some Ics are designed to accept both types; others accept only one type. In either case, the closed keypad contacts give an indication of the key being depressed. In some cases, the closed contacts may apply a supply voltage on the output lines for as long as the key is held down. In other cases, a ground or the common side of the power supply may be provided. The keypad may be arranged to provide only a pulse, as is the case for a keypad that is used with a scanning sequence. The output waveform are shown in Figure C-13b.

Figure C-13. Keypad Contact Types and Output waveform

Figure C-13a Figure C-13b

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5. Protection Circuit

5.1 Overvoltage Protection

The electronic circuits are protected from high voltage spikes on the line by zener diodes.

Figure C-14 Overvoltage circuits

5.2 Polarity Protection

Polarity reversal is prevented by the rectifier bridge.

Polarity of the normal input voltage is critical for electronic circuits since they won't operate if the polarity is reversed, and they may be damaged. The method commonly used to protect against polarity reversal is the rectifier bridge. The output voltage polarity of a rectifier bridge is always the same regardless of input voltage polarity.

For line voltage of less than 5 volts, the low-voltage rectifier bridge is used. Its forward voltage drop is low because the conducting transistors are at saturation. The transistors are subject to voltage spike damage, however, and are therefore protected by Zener diodes.

6. MC145416

6.1 SWITCHHOOK

6.1.1 On-Hook

Figure C-15 is a block diagram of a telephone set which shows the major functions. The ringer circuit, which will be discussed later, is always connected across the line so it can signal an incoming call. The remainder of the telephone set is isolated from the line by the open contacts of the switchhook when the handset is on-hook. No dc flows (except possibly a small leakage current) since the ringer has a capacitor that blocks dc flow through it.

Figure C-15 Dialer set Block Diagram

6.1.2 Off-Hook

In the off-hook condition, the closed switch-hook contacts begin a sequence of events in the central office. Initially a relay is energized and a line searcher finds the off-hook line. Then a connection is established, sending a dial tone.

Figure C-16 Line interface relay operation

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6.2 Dial interface

The Motorola MC145416 contains a tone amplifier and interface circuit designed to connect dialing signals directly to the loop. Figure C-17 is a diagram of the dial interface. Pin 11 (MS) is a mode select input which switches the mute logic between tone and pulse dialing modes. In this way, the circuitry can provide the appropriate muting signals for tone or pulse dialing. Mode selection must also be connected to the respective dialing circuit.

The mute signal from the dialer is sent to pin 12 (MO). It is this input which supplies the logic control signal the at mutes the receiver. Tone dialing signals can be connected directly to pin 19 (DTO). These signals will be amplified directly by the dial amplifier, A_D, and sent along to the local loop.

Figure C-17. Dial Interface

Redial function

With the memory function available, it was relatively easy to incorporate a redial function. By pushing only one button, the last number entered will be redialed. This feature is helpful when continually trying to reach a busy number. Initially, the redial feature met with some resistance from the telephone companies because of fears of clogging the network since redialing could be done so rapidly and frequently. also, they were concerned about the maintenance of batteries used to power the electronic circuits in the telephone set. The development of complementary metal-oxide-silicon (CMOS) semiconductor technology, which produces integrated circuits with very low power consumption, has solved the latter problem. The current drain of these circuits is only a few micro-amperes so that it is possible to operate the electronics from the dc power available from the telephone line. However, if a battery of the type commonly used to power calculators or other consumer electronic goods were used to provide only the very small current required by the number memory, the battery would last for several years.

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Users Manual

A. Manual Dialing - OFF-HOOK D1 ------------ DN

1. Dialing Tone (DTMF) output will continue as long as a valid key is depressed.
2. Mode change can be set on- or off-hook before keyboard entry.
3. In Tone Mode
   1. All digits, including * and #, will have DTMF output.
   2. All digits, including * and #, and Pause will be stored in the LNR register.
   3. Flash, PS/S, MS (Memory Store), and MR (Memory Recall) will cause a PTO output to be generated as long as a key remains pressed.
4. In Pulse Mode (10 or 20 pps)
   1. Numeric input 0-9, Pause, and PS/S will be stored in the LNR register.
   2. Number inputs 0-9, * and #, Flash, LNR, PS/S, MS, and MR will cause a PTO output to be generated for as long as the key remains pressed.

B. Last Number Redial - OFF-HOOK LNR/PS

When this is the first key depressed after off-hook, excluding Mode Select Switch, it causes the last number entered from the keypad to be dialed out.

1. Mixed dialing from the keypad can be stored and redialed with pulse to tone mixed dial out or can be converted to all tone with the Mode Select Switch, retaining the four second pause.

ENTERED ......

Mode Select Switch to Pulse Mode, ENTER;

D1 --------- D PS/S D ---------- DN

Pulse input Mode DTMF input

Change with pause

REDIALED ......

ON-HOOK to OFF-HOOK

Mode Select Switch in Pulse Mode, ENTER;

LNR/PS ,Dial out is the same as original entry.

REDIALED ......

ON-HOOK to OFF-HOOK

Mode Select Switch in Tone Mode, ENTER;

LNR/PS ,Dial out changes to"

D1 --------- D D ---------- DN

DTMF input PUSE DTMF input

1. Numbers dialed from memory 1-9, and N1, N2, and N3 will not be stored in the LNR register.
2. Numbers stored with the MS pin set to DTMF cannot be converted to pulse with the PS/S key because the part does not know to go to 10 or 20 pps.

C) Dialing with auto access pause - OFF-HOOK

ENTERED ......

Mode Switch in either Pulse or Tone Mode

D1 --------- D LNR/PS D ---------- DN

REDIALED ......

ON-HOOK to OFF-HOOK

Mode Select Switch Unchanged, ENTER;

LNR/PS ,Dial out is the same as original entry.

D1 --------- D PAUSE D ---------- DN

1. Pause is stored in a data number sequence by pressing the LNR/PS key during keypad entry.
2. More than one pause can be entered in sequence for extended pauses.
3. An indefinite pause duration can be provided with a custom metal option.
   1. The indefinite pause will not occur during normal tone or pulse dialing.
   2. On redial, this pause can be terminated by pressing any other key.

D) Dialing with auto access pause and mode change - OFF-HOOK

ENTERED ......

Mode Select Switch in Pulse Mode (10 or 20 pps)

D1 --------- D PS/S D ---------- DN

Pulse Dialing Mode Tone input

Change with pause

ENTERED ......

Mode Switch in Tone mode

D1 --------- D PS/S D ---------- DN

Tone Dialing Pause Tone input

Change with pause

1. Dialing in the Pulse Mode and depressing the PS/S key will initiate a four second auto access pause with the mode change to DTMF.
2. Starting in the Tone Mode, depressing the PS/S key will not cause a mode change to occur, but will insert a four second pause in the dial sequence.

E) Memory storage and recall - OFF-HOOK

1. A total of 18 digits can be stored.
2. Pause and Mode Switch (PS/S) key each count as one digit.
3. After pressing MS (Memory Store) key, all outputs are inhibited accept the PTO output. Succeeding numeric inputs including PS/S, are counted as data. Following the second MS (Memory Store) key input, the first numeric input is counted as address (A= 1-9 or N1, N2, or N3). Any non-numeric key entered. including 0, will be ignored, and the part will wait for another entry.

REDIALED ......

a) Mode Select Switch in Pulse Mode (10 or 20 pps)

Memory Store Sequence ......

MS D1 ------ D PS/S D ------ DN MS A

Pulse mode Mode Tone mode A = 1-9

Change with pause or N1, N2, N3

ON-HOOK to OFF-HOOK ENTERED ......

Memory Recall Sequence ......

MR A A=1-9 Dial out is: D1 ------ D D ------ DN

Pulse mode Mode Tone mode

Change with pause

b) Mode Select Switch to DTMF

Memory Recall Sequence ......

MR A A=1-9 Dial out is: D1 ------ D D ------ DN

Tone mode Pause Tone mode

REDIALED ......

a) Mode Select Switch in Tone Mode

Memory Store Sequence ......

MS D1 ------ D PS/S D ------ DN MS A

Tone mode Pause Tone mode A = 1-9

Change with pause or N1, N2, N3

ON-HOOK to OFF-HOOK ENTERED ......

Memory Recall Sequence ......

MR A A=1-9 Dial out is: D1 ------ D D ------ DN

Tone mode Pause Tone mode

b) Mode Select Switch in Pulse Mode (10 or 20 pps)

Memory Recall Sequence ......

MR A A=1-9 Dial out is: D1 ------ D D ------ DN

Pulse mode Pause Tone mode

Change with pause

1. Number storage during conversation is allowed by following the above procedure.
2. Memory registers can be programmed sequentially without going on-hook between each entry.

F. Cascaded dialing - OFF-HOOK

1. Memory cascaded

a) Numbers stored with the Mode Select Switch set to pulse (10 or 20 pps) can be dialed out as follows:

ENTERED ......

ENTERED ......

ENTERED ......

1. Cascade dialing can be accomplished from any memory location in any order, including LNR ......
2. Numbers stored with the Mode Select Switch set to pulse (10 or 20 pps)

ENTERED ......

ENTERED ......

4. The second control key, or number input, has to be entered after completion of the previous dialing.

G. Flash - OFF-HOOK FLH

1. Pressing the FLH key will cause a 600-ms pulse to be generated at the pulse output pin. This pulse will not be stored in either the LNR register or the memory registers. The mute output will go low for 600 ms and the PTO output will be active for as long as this key is depressed.

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Digital playback/record unit

Illustration of Digital playback/record unit

Operation Principal

We would like to separate this section into two parts:

1. Circuit operation.
2. ISD 1416 ChipCorder® technology.

Schematic Circuit Diagram

See Appendix D-1

Printed Circuit Board

PCB Layout

The detailed PCB layout such as shield screen, bottom layer, top lay, etc. it also consists of different scaling 1:1 and a fit to page printout, easy read the PCB in a relative large size, please see Appendix D-2 page 1 through 13.

PCB Specification

Specifications for D:\PROJECT\DIGITA~1\RPPROJEC.PCB

On 6-Apr-1997 at 17:20:17

Size of board 0.301 x 0.375 sq. in

Equivalent 14 pin components 1.520 sq. in/14 pin component

Components on board 28

Layer Route Pads Tracks Fills Arcs Text

Top Layer Vertical 0 228 0 0 0

Bottom Layer Horizontal 0 255 0 0 0

Top Overlay - 0 170 0 4 0

Multi-Layer - 104 0 0 0 0

Total 104 653 0 4 0

Layer Pair Vias

Top Layer - Bottom Layer 17

Total 17

Hole Size Pads Vias

28mil (0.7112mm) 5 17

32mil (0.8128mm) 99 0

Total 104 17

Circuit Operation

For detailed pins description please refer to appendix D-3. The data sheet shows the detailed description of ISD14xx series and 10xx series chips.

Playback looping

ISD 1416 supports several operational modes as follows:

For our special purpose, we would like to choose A3 - Looping mode for message continuously playback. So, the ISD 1416 pin 4 (A3), 9(A6) and 10 (A7) are pulled high after message recorded, it should be noted that A3 and A6 pulled high indicates the chip running in the operational mode and the addressing mode. In order to achieve the such mode, a 3 pins jumper S1 employed that pull the such three pins high while either playback or standby and low while recording.

In order to obviously demonstrate the digital recorder unit, our prototype unit connected an 8W speaker permanent to the sp+ and sp- pins through two 18W resistors (R8, R9) in parallel (impedance matching purpose, (18//18)+8=17W , the rated output impedance be at least 16 W.) and a dip switch that control the PLAYE* pin connected to either ground or Vcc, since the signal triggered by a negative going pulse, not the voltage level, a micro switch would more suitable for the purpose. But we get a four switches dip switch, we prevent the waste of components, using that instead of the micro switch. There are two different mode of playback triggering method we can use, the level trigger and the edge trigger. We chose edge trigger because it easy interfacing so that increasing the connectivity and future expansion of our project, so we connected the PLAYL* always to Vcc. And use the PLAYE* input as the trigger pin. By switching on and then of the dip switch S2-sw3 (simulate a negative going pulse), the automatic playback looping commence until:

1. Power cuts-off
2. REC* pin receives logic 0. (REC* with the top priority, once REC* triggered, other operation would stop and the recording process commence immediately)

According to the purpose we required, there is no need to stop the playback process once it triggered.

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Message Recording/normal Playback

All address pins A0 through A7 are pulled low for recording mode. By connecting with a telephone, the Microphone section can be totally eliminated, and then connect the microphone of telephone handset directly to 1416 ANA IN pin (pin 20). Therefore, we can eliminate MC1, C3 - C6, R2 - R5, quite reduce the manufacturing cost. In fact, there are some interfacing circuit may be need to match the handset microphone and the 1416 ANA IN pin input characteristics. For demonstration purpose, we add all of such components to show the demo unit easily. The C4, C5 MC1 are tied together and then connected to MIC and MIC REF pin of 1416 carried out the following purpose:

1. MIC REF is an inverting input to the microphone preamplifier that eliminates noise.
2. The capacitor value, together with the internal 10KW resistance on this pin, determine the low-frequency cut-off for the 1416 passband. By calculation and practice, (fc=1/2RC=1/210K*0.1u200Hz for C=0.1uF and fc=1/2RC=1/210K*0.01u600Hz for C=0.01uF) So, we change the capacitors' value from 0.1uF to 0.01uF to increase cut-off point of lower frequency that let the playback sound seem louder.

R5, C6 give the time constant for the release time and an internal 5K resistance and C6 give the time constant of the attack time, by calculation, 5K*4u7=23.5mS, say the gain would pulled-down within 23.5mS when a louder sound attacked. On the other hand, by employed the R5, a 470KW resistor, applied the formula above, we got 470K*4u7=2.209S, say the gain would gradually increase within approximate 2.2 seconds, the release time quite longer than the attack time because sound usually decrease in a slow gradient while the sound sudden increases. They help the AGC dynamically adjusts the gain of the preamplifier to compensate for the wide range of microphone input levels. Allows full range of sound to be recorded with minimum distortion.

In order to prevent unexpected recording taking place when circuit is powered up or Vcc rises faster than REC*. This undesired recording prevents playback of the previously recorded message. A spurious End Of Message (EOM) marker appears at the very beginning of the memory, preventing access to the original message, and nothing is played. To prevent this occurrence, we place C7 between the control pin (REC*) and Vcc. This pulls the control pin voltage up with Vcc as it rises. Once the voltage is HIGH, the pull-up device will keep the pin HIGH until intentionally pulled LOW, preventing the false EOM marker.

An LED (D1) in series with an R7 (1K) resistor (current limitation) connected to RECLED* to indicate that the recording process taking place.

The whole circuit operation please refer to the following flow chart:

ISD 1416 ChipCorder® technology

Pin assignment of ISD 1416:

The ISD1416 ChipCorder® devices is controlled by a single record signal, REC*, and either of two playback control signals, PLAYE*, and PLAYL*.

ChipCorder^® technology provides a means of storing information directly, without conversion to digital, into standard EEPROM memory cells. Utilizing a patented multi-level storage technique, the devices currently store up to eight times the information per memory cell compared to conventional digital solutions.

Since EEPROM cells are non-volatile, 1416 does not require battery backup to preserve the recorded message. Overall power consumption, therefore, is dramatically reduced.

The most different between ChipCorder^® technology and traditional AD/DA technology is that enables storage of analog signals directly into memory, eliminating the need for analog-to-digital conversion. This not only minimizes, but also simplifies, the external circuitry required. Furthermore, 1416 also integrated the oscillator, microphone pre-amplifier, AGC, antialiasing filter, smoothing filter and speaker amplifier on-chip, quite reduces the circuit complication.

1416 using "Multi-level" storage that is a high-density storage methodology. Conventional digital storage, for example, stores one "bit" of information per memory cell - a "1" or a "0" (or, in terms of voltage levels, an "on" or an "off"). 1416 improves on this and stores up to 256 distince voltage levels per single cell! So, 1416 is able to store up to 8 times (2 to the power of 8 = 256) more information in the same amount of memory space.

Actually, 1416 enables small packets of charge to be pulsed in a controlled manner through the oxide into the floating gate in the storage cell. Digital solutions, in comparison, drive a tremendous amount of charge through the oxide all at once, literally causing much greater "wear and tear" on the thin gate oxide. ISD's storage implementation, therefore, provides much greater reliability and a higher number of record cycles over conventional storage devices.

Internal block diagram of 1416/20 series:

Testing Procedures:

1. set the switch as follows,

2. Red LED lights, recording process commencing …

1. Record 16 seconds (fully filled the capacity) message, observe the REC LED, it would off when memory full. Otherwise, fail this unit.
2. Turn S2 sw4 OFF.
3. Switching the S2 sw3 (put it on then off immediately) to hear the message you recorded previously. If the quality not accept, take it out.
4. Repeat the step 1 through step 2, record an episode around 10 seconds then turn S2 sw4 OFF.
5. Turn S2 sw4 OFF.
6. Switching the S2 sw3 (put it on then off immediately) to hear the message you recorded previously. If the quality not accept, take it out.
7. Short S1 1-2, switching the S2 sw3 (put it on then off immediately to manually provides a negative going pulse) to hear the message you recorded previously, it will playback continuously, otherwise, take it out.

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Users Manual

Recording message

1. set the switch as follows,

2. Red LED lights, begin recording message …

1. when the desired message recorded, turn S2 sw4 OFF. There is an exception, should your message longer than 16 seconds, the unit would automatically power down (LED off), in this situation, you are also required to turn S2 sw4 OFF as normal stop.
2. Switching the S2 sw3 (put it on then off immediately) to hear the message you recorded previously.
3. Should you unsatisfied the message due to any reason, repeat the step 1 through step 4.
4. Short S1 1-2 and now, the unit is ready for use to playback during connection established.

It should be noted that since there unit store the message in an advanced technology, there is no need to connect power to retain the message you recorded.

Message Playback

Since the auto dialer would automatically triggered the unit to play your message recorded, should you will not need to do anything once you recorded the desired message.

Should you want to revise the message, do not worry! It is able to re-record up to 100,000 times.

Should you have any question please do not hesitate to contact us.

Testing Report Document

See appendix D-0

Specification of Digital Recorder

Service Manual

Bill of Material and the raw material cost (estimated)

D:\project\report writing\Digital Recoder BOM.xls

Design episode:

Initially, we received the original idea for construct the digital recorder by using ISD 1016/1020 from the friend of Internet. After visit the Information Storage Device Corporation's wet site, we got the data sheet of 1016/1020 and 2590 chips and found also that there are two local distributors existed. Since there is few time for us to construct digital recorder, we design the circuit while trying to find the 1016 chip. 2 weeks hard working later, we complete the circuit design. Unfortunately, 10xx series have been phase-out this year, yet! All design becomes garbage! At that time, we remember that our friend Mr. John said, 'find the parts first, never design before the parts found!' But too late!

Fortunately, Mr. Wong suggested us to change to use 14xx series, and this time, we try to buy the chip first and then start the design process.

This lesson told us that whenever we construct a project, find the material required first then doing the construction.

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Remote Control Section

Auto dialer section

Digital Recorder Section

PCB Design and UHF Remote Controller

Initially, we used universal PCB to implement the receiver, transmitter and decoder, since wire-wrap wire not fixed on the PCB, resulted that the circuit operation quite unstable.

In order to eliminate the such problem, we made the PCB ourselves. At that time, we just route the traces as normal PCB design, the wire turned 90 degrees. Although, we got the better results than the initial one, but it still seems unstable, and we found the additional problems that the gain of op-amp is unsatisfied, the gain too small to amplify the signal received, Our project supervisor Mr. Poon suggested that the uA741 unstable for single voltage source configuration, should we change another one might carried out the satisfied results. Furthermore, the turns of antenna on receiver insufficient that significantly distorts the UHF signal transmitted from transmitting end.

From the study of the subject - Electronic Design Automation, we knew that the design methodology of high speed PCB significantly different from the normal (low frequency, i.e. frequency lower than 20MHz) PCB design, the 90 degrees turning point leads a major problem that just like an antenna to emit the high frequency, and the such frequency would interfered the surround circuit resulted in circuit unstable and eventually suspend the circuit. So, we change our PCB layout again that all turning point change to 45 degrees instead of the 90 degrees turning previously, and change also the op-amp from uA741 to MC4558 which supports a single positive voltage supplied.

Auto Dialer

At the final, this a auto dialer can not completely successful. We think that there are product many problem, as shown in the following ?

1. Be unable to detect busy tone ?
2. Interfacing between TP5700A and MC145416 have some unexpected problems that caused the TP5700A functional problem ?

Firstly, we must know that the auto dialer sets like those used to dial a number or more calls, the receiver have be switchhook (on- or off-hook). We have know a information that as the follows points. It is simple in appearance and operation yet it performs a surprising number of functions. The most important ones are:

1. It requests the use of the telephone system when the handset is lifted.
2. It sends the number of the dialer to be called to the system. This number is initiated by the caller when the number is pressed or the dial is rotated.
3. It indicates the state of a call in progress by receiving tones indicating the status (ringing, busy, etc.).
4. It indicates an incoming call to the called telephone by ringing bells or other audible tones.
5. It changes speech of a calling party to electrical signals for transmission to a distant party through the system. It changes electrical signals received from a distant party to speech for the called party.
6. It automatically adjusts for changes in the power supplied to it.
7. It signals the system that a call is finished when a caller "hangs-up" the handset.

The principle of the how to detect busy tone that first we must know the central office how working ?

The central office must provide the ringing signal to the subscriber telephone to alert the called telephone that a call is waiting; therefore, the central office must apply the ringing signal to the line after the switching has completed the connection. This is done normally by a relay that is energized by the switch. The ringing signal is typically 90V rms. at 20Hz.

Detecting service requests (when the caller goes off-hook), the dialing input, and supervising calls in progress (when the ring is answered, or when either party hangs up) are accomplished by detecting the presence or absence of current flow in the loop. The requires a sensor that can discriminate accurately, regardless of line length, between off-hook current and current as a result of noise, leakage or a small standby current for the memory in an electronic dialer circuit. There are two common methods used for detecting a subscriber off-hook - loop start and ground start.

Loop start lines are used in the vast majority of local loop circuits; they signal off-hook by completing a circuit at the dialer. Figure C-16 illustrates a subscriber line interface using relays for sensing and logic. In the on-hook condition, neither the line relay nor the cut-off relay is operated, and the line relay battery provides power to the line. No current (except perhaps leakage current) flows because the switchhook contacts are open.

When the subscriber lifts the handset (Figure C-16a) current flows from the line battery through the closed switchhook contacts and energizes the line relay. A set of the line relay contacts close to signal the switching circuits, via the line finder, that the subscriber wishes service. When the line finder seizes the line to provide dial tone, it causes the cutoff relay to operate, which disconnects the line relay as shown in Figure C-16b, and extends the circuit into the switching equipment. This also disconnects the line battery so further operation is powered by another battery supply through the first selector or register of the switching system. Note that the line relay has two windings, one connected in each side of the line. The windings are balanced and wound so that voltages induced in the line are canceled; thus, only current that flows around the entire loop will cause the relay to operate.

Ground-start lines are used on loops connecting PBXs to the central office, and in other situations where it is desirable to detect a line that has been selected for use (seizure of the line) instantaneously from either end of the line. Grounding the ring-side path, as shown in Figure C-18, causes current to flow through one-half of the line relay which is sufficient to energize the relay. Further operation is as explained for loop start. When dial tone is detected by the PBX equipment, the ground-start contact is opened.

Appendix C Figure C-18 Ground-Start Signaling

The central office supplies the ringing signal. Service requests are detected by the presence or absence of current. A sensor monitors the line loop current, and detects significant changes. Two methods are used - loop start and ground start.

In loop start detection, a cutoff and line relays are used for sensing and logic. The line relay is energized when the switchhook contacts are closed. The line relay is disabled by the activation of the cutoff relay.

In ground start, the line relay may be activated by grounding the ring side of the line at any point. This configuration is usually used with PBX equipment.

Digital playback/record Unit

Why choose ISD 1416P

1. Non-volatile memory avoid power failed missing message.
2. Less components used, resulted in Small size, high integration. No external memory needed. For traditional digital recorder circuit, there are at least two DRAM chips employed.

Easy interface: The playback function can easily achieved by using either a falling edge or a low level.

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This project carried out an unexpected problem. We are unfamiliar in telecommunication circuit design, so the auto dialer cannot meet the proposal we submitted. According to the proposal, the auto dialer be able to detect the busy tone / pickup and then dial another party. As the specification of IC MC145416 used, it is able to dial 3 different parties one by one as the previous number unsuccess to connect. The detailed episode during constructing auto dialer, please refer to discussion section.

There is an very important thing that the operating frequency may jam other government department infracommunication, such as police communication, so the Life-Saver must apply an approval before mass product to prevent that offend the law.

The Life-Saver we constructed adopt many future expansion functions for further purpose.

As the Life-Saver carried out dramatic features, functionality and flexibility, we have the confidence that it would got large market share and since we tried the best to reduce the cost (overall raw material cost only HKD137.64), resulted in lower retail price, it does not only strong the competitive but also provide benefit to elder.

This project not only help us engaged the theories from books and the practical design constrains, but also do a meaning thing to the society to help the senior citizens. Do not forget, we living in this prosperous land, because their hard working throughout the life yesterday!

Furthermore, we drafted a case for finished product, please see the appendix Z-1 and Z-2.

Understanding Telephone Electronics

3^rd Edition

Stephen J. Bigelow

Motorola at

http://www.mot.com

National Semiconductor Corp.

http://www.national.com

Information Storage Devices Corp.

http://www.isd.com

It available on Internet at:

http://www.ho.com.hk

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