Greetings. Great stuff and work! I noticed you have a very old copy
of the DTMF FAQ (0.1) Here's 1.0:
-------------chop-with-axe----------------chop-with-axe---------------------
TELEPHONE TONE DIALING CHIPS
Author : T.H. Tsim
Version: 1.0
Date : August 25th, 1994
E-mail : tsjoit@solist.htsa.hva.nl
Contents:
1. Short introduction to DTMF
2. List of DTMF-receiver chips
3. An alternative approach: DSP
4. Conclusion
_________________________________________________________________
Hi! After reading sci.electronics for a couple of years, I've
discovered that many people are interested in decoding DTMF-signals
for various applications. A frequently asked question (FAQ) concerning
this subject is: "What IC should I use in order to decode DTMF
signals?"
_________________________________________________________________
1) Short introduction to DTMF
DTMF means: Dual Tone Multiplexed Frequency, the tones you might have
heard while pressing the keys on your telephone. Each key produces a
slightly different signal, which is a mixture of two frequencies, i.e.
pressing '1' will send a tone made of 1209 Hz and 697 Hz to the other
end of the line.
1209 Hz 1336 Hz 1477 Hz 1633 Hz
ABC DEF
697 Hz 1 2 3 A
GHI JKL MNO
770 Hz 4 5 6 B
PRS TUV WXY
852 Hz 7 8 9 C
oper
941 Hz * 0 # D
There are many ways to detect and decode these DTMF tones. One idea
could be an eight sharp-tuned filter combination with detection
circuits. Needless to say, this is very impractical, considering the
various ICs (Integrated Circuits or 'chips') made by different
manufacturers all over the world.
Most of these ICs do not require more than one (inexpensive) 3.58 MHz
x-tal or resonator and the power circuitry. Usually the output is
4-bit binary + 1 strobe.
--------------
l l- d3
l DTMF l- d2
signal in -l Decoder l- d1 4-bit binary out
l chip l- d0
l l- strobe
--------------
Note: This figure is merely for decoration, it does not imply package
information
Nice text to read about DTMF and telephony can be found in:
"Understanding Telephone Electronics"
Howard W.Sams & Co
ISBN: 0-672-27018-18
2) List of DTMF-receiver chips
The companies are listed in a random order:
Silicon Systems Inc.
SSI202 DIP-18
SSI203 DIP-18
SSI204 DIP-14
All req. 3.58 MHz (3.579545 MHz) crystal
{ Added note from ftp site ftp.armory.com pub/user/rstevew for the }
{ devious at heart!!: If you replace the 3.579545 MHz used in many }
{ DTMF ENcoders, as well, by a 6.553600 MHz crystal, a key on your }
{ dialer will make a sound surprisingly identical to the tone that }
{ pay-phones interpret as a coin! This info is for the technically }
{ curious and does not constitute a conspiracy by me with folks to }
{ engage in theft of service, no matter how much it seems to!! ;-> }
A neat and well documented design + PCB layout by Tom Miller KA1JQW,
can be found in "The ARRL handbook for radio amateurs", ISBN:
0-87259-169-7
Crystal Semiconductor Corp.
CS20x family
OKI
MSM6843 DIP-28, 3.58, 4b1s
Application note in OKI Telecom LSI data book
Motorola
MC145436
MC68HC05F5
(From Arkady Horak-Systems)
I spent about the last 14 months of my life working on an integrated
DTMF receiver here at Motolora and I would like to have you add the
part to the DTMF-list. The receiver is part of a 6805 8-bit
microcontroller and is called the MC68HC05F5. Here is a quick feature
list:
* MC68HC05 based core micro
* Memory mapped I/O registers
* 5632 bytes of user ROM
* 224 bytes of RAM
* 15-bit multi-function timer
* Power saving STOP, WAIT and Data-Retention modes
* Mask optional COP (computer operating properly) or watchdog timer
* Self check ROM
* Fully static operation with no minimum clock speed
* 30 bidirectional I/O pins
* On chip oscillator for use with external crystal or ceramic
resonator 2 or 4 MHz operation only while DTMF rec. is functioning
* DTMF receiver
* 40 pin plastic dip or 44 pin plastic leaded chip carrier packages
Being an avid electronics hobbyist I feel this part will see a lot of
service in hobby applications. This part is, to the best of my
knowledge the first general purpose microcontroller with an integrated
DTMF receiver. Currently only a ROM based version is available but as
sales grow a 705 or EPROM version may be manufactured. Also, this part
is compatible with the 6805 development tools and software.
Arkady Horak <ark@oakhill-csic.sps.mot.com>
Motorola CSIC Microcontroller Division
Austin, TX
Teltone
M957-0x DIP-22 or SOIC-24, 4b1s, 5 and or 12 Volt (read below)
CAUTION: M957-02 and M957-01 differ in operating voltage!, M957-01 can
operate from 5 - 12V, M957-02 operates 5V only (not suitable for 12 V
apps!)
A ready to build schematic by R.G. Krijgsman based on this Teltone
M957-2 chip can be found in: "Het Elektuur telefoonboek" ISBN
90-70160-94-3, (Dutch language)
Unknown
KT3170 DIP-18, minimal ext. parts ?
UMC, United Microelectronics Corp.
UM9203 DIP-18 4b1s and 2of8
UM9204 DIP-14
UM92870A/B/C DIP-18 (three variants)
Examples of line-interfaces and app-notes in the UMC communications
ICs databook.
Mitel Corp
MV8870
Note: Teltone seem to carry this type-number as well.
Toshiba
TC35301AP DIP-28, 4b1s
Harris
CD22202 DIP-18, 4b1s
CD22203 DIP-18 4b1s and 2of8
CD22204 DIP-14 or SOIC-24, 4b1s
Legend:
3.58 = an inexpensive 3.58 MHz needed
4b1s = 4-bit 1 strobe output (Hexoutput)
2of8 = 2-of-8 code
3) An alternative approach: DSP
Another way to decode/produce DTMF signals is by applying a DSP, a
Digital Signal Processor. Practical examples of such an approach can
be found in the TMS320 BBS, which is currently being mirrored at
ti.com /mirrors/tms320bbs.
files of interest concerning this faq are:
TEL-2-1.EXE 57K | DTMF Encoder/Decoder for C3x by DSP
TEL-2-2.EXE 53K | DTMF Detection Data Sheet by Ensigma Ltd.
DTMF10.EXE 24K | TMS320C10 based DTMF decoder
DTMF10E.EXE 19K | TMS320C10 based DTMF encoder
DTMF_C17.EXE 126K | TMS320C17 based DTMF encoder/decoder
Link to /mirrors/tms320bbs directory
Link to /mirrors/tms320bbs Index
_________________________________________________________________
4) Conclusion
Well, that's the latest I've found on DTMF receivers. There are no
doubt other companies producing these kind of chips, so please let me
know and I'll improve this list (when I've got the time)
Unfortunately, I'm not that experienced yet to answer any difficult
technical questions about this subject.
For suggestions, improvements, info, flames, waterbuckets (?) please
e-mail me at: tsjoit@solist.htsa.hva.nl.
I graduated July 1st 1994, so I won't continue writing updates for
this faq (no time, no space, no money :)
I like to thank all of you who think this faq was usefull, especially
the ones who wrote me e-mail . I was very suprised to see this faq
appear in the most strange places on the Net :)
Anyway...have fun with those di-du-dit-di-duh tones :)
------------chop-with-axe----------------chop-with-axe---------------------
+-->Filip "I'll buy a vowel" Gieszczykiewicz | E-mail: filipg@paranoia.com
| NEW ADDRESS! http://www.paranoia.com/~filipg | SCI.ELECTRONICS FAQ + MORE!
| Enjoy your job, work within the law, make lots of money : Choose any two.
| Making money with CS and spending it on robotics, life & friends. !NOT(!PC)
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