MICROCONTROLLER BASED TELECOM SWITCH

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MICROCONTROLLER BASED TELECOM SWITCH

• SPONSORED BY ARJ ASIA
• External Guide Mr. Jitendra Date
• Internal Guide Mr. M.B. Tirmare
• By Neha Purandare
• Janhavi Shah
• Sonali Shelke

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PROBLEM A "telephone
solicitation" is a telephone call that acts as an
advertisement. Even if you have an unlisted,
non-listed, or non-published telephone number,
you may still receive unsolicited telephone calls
with automated or prerecorded messages. In some
cases unlisted or non-listed numbers can be
obtained from a directory assistance operator.
They, along with non-published numbers, may be
sold to other organizations or people with whom
you have done business. Some sales organizations
call all numbers in numerical order for a
neighborhood or area. SOLUTION In
the field of telecommunications, a telephone
exchange (US telephone switch) is a piece of
equipment that connects phone calls. It is what
makes your phone calls "work" in the sense of
making connections and relaying the speech
information. Here we are  using our telecom
switch to connect only the right call and block
the unwanted ones.
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BLOCK DIAGRAM
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EXPLANATION OF BLOCK DIAGRAM
DTMF Encoder The DTMF encoder
resembles the telephone set. It uses DTMF encoder
integrated circuit, Chip UM 91214B . This IC
produces DTMF signals.
DTMF Decoder It consists of
MT8870D chip which is a direct DTMF detector. Its
output is a 4- bit BCD code each 4 bit code
corresponding to a DTMF tone pair. Whenever a
valid tone pair is detected at the input, the StD
pin goes high indicating that the tone pair has
been latched.
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• Microcontroller
• PIC18F452 accepts the 4 bit BCD
  code from MT8870D and checks if the DTMF tone
  pair stands for numbers between 0 to 9. If it
  does, it is considered a valid no. and the user
  is allowed to receive the call else it is routed
  to voice chip and rejected.

ISD2560 Voice chip If the call is
unsolicited one, the P/R bar pin of this chip is
pulled to Vcc and a message rejecting the call is
played back to the caller. The message is
pre-recorded on the chip by manual switching of
P/R bar and CE bar pins.
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Features of PIC18F452

• 16-bit wide instructions, 8-bit wide data path

Linear program memory addressing to 32
Kbytes Linear data memory addressing to 1.5
Kbytes

• 100,000 erase/write cycle Enhanced FLASH
  program
• memory typical
• 1,000,000 erase/write cycle Data EEPROM
  memory.
• Low power, high speed FLASH/EEPROM
  technology.
• Wide operating voltage range (2.0V to 5.5V)
• Watchdog Timer (WDT) with its own On-Chip RC
  
• oscillator for reliable operation.
• Programmable code protection

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Features of MT8870D

• DTMF Receiver
• Low power consumption
• Internal gain setting amplifier
• Adjustable guard time
• Central office quality
• Power-down mode
• Inhibit mode

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FEATURES OF ISD2560

• Easy to use, voice
• record/playback solution.
• Single chip with 60 sec duration
• Manual switch or uC compatible.
• Auto power-down (push-button)
• mode
• Can handle multiple messages
• On-chip clock source
• Single 5 volt power supply

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FLOWCHART
START

ACCEPT INPUT TONES FROM MT8870D
IS StD1?
N
Y
A
10
A
IS TONE BET 0 TO 9?
N
MAKE RD0 1
Y
MAKE RD1 1
STOP
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SOFTWARE

• Development Environment
• The MPLAB C18 Code Development
  Systems are complete ANSI C compilers for
  Microchips PIC18CXXX family of microcontrollers.
  This compiler provide powerful integration
  capabilities and ease of use not found with other
  compilers.
• Programmer PICSTART Plus Entry Level
  Development Programmer
• The PICSTART Plus development
  programmer is an easy-to-use, low cost, prototype
  programmer. It connects to the PC via a COM
  (RS-232) port. MPLAB
• Integrated Development Environment software
  makes using the programmer simple and efficient.
  The PICSTART Plus development programmer supports
  all PICmicro devices with up to 40 pins.