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  1.  
  2.             -= H A C K E R S =-
  3.  
  4.                            Issue #8,  File #4 of 9
  5.  
  6. ***************************************************************************
  7.                       D T M F   S C A N N E R
  8. ***************************************************************************
  9.  
  10.                                   By:  Jojo
  11.  
  12. This article gives descriptions and plans for building a small electronic
  13. circuit that reads digits dialed on a phone line. I made it all up myself
  14. so u won't find anything about it in books; it works fine, I sold a lot
  15. of these devices to friends.
  16.  
  17. If u already have experience in building electronic circuits then u will
  18. find this circuit very easy to build: two graphic files (DTMF.BMP and
  19. DTMFPCB.BMP) give circuit diagrams *and* printed circuit board layouts :-)
  20.  
  21. If u r a beginner and want to learn about building an electronic circuit
  22. using the printed circuit board layouts, just print the graphic file
  23. DTMFPCB.BMP and take it to an electronic components shop. They will
  24. tell u how easy it is to use those layouts: they can make the board
  25. for u for less than $10, then all u'll have to do is soldier the
  26. components on it.
  27.  
  28. If u just want to know more about how a digit is dialed on a phone line
  29. then read the "how does it work?" part.
  30.  
  31.  
  32.  
  33.  
  34. W H A T ' S   A   D T M F   S C A N N E R   ? :
  35. -----------------------------------------------
  36.  
  37. It's an electronic device that connects to a phone line and reads the
  38. digits dialed on it. DTMF stands for: Dialing Tones using Multiple (or
  39. Modulated) Frequencies. The scanner described here can be used in 2
  40. different ways:
  41.  
  42. 1.      PHONE LINE --> DTMF SCANNER --> YOUR EYES
  43.         The scanner has LEDs (Light Emitting Diodes) on it; when a
  44.         digit is dialed on the phone line, some of these LEDs will
  45.         light, others won't, depending on which digit is dialed. So
  46.         you can "read" the digits just by looking at the LEDs :)))
  47.  
  48. 2.      PHONE LINE --> DTMF SCANNER --> COMPUTER
  49.         The scanner can also be connected to the Centronics interface
  50.         of a computer: the centronics is the 25-pins connector at the
  51.         back of your computer that is usually used for connecting a
  52.         printer.
  53.  
  54.         The computer then uses a little program to read the signals
  55.         received on the Centronics interface and display the digits
  56.         dialed on the phone line. These digits can be saved in a file.
  57.  
  58.         NOTE: this scanner uses special electronic components called
  59.         opto-isolators that ELECTRICALLY SEPARATE the signals on the
  60.         computer side from the signals produced on the scanner side.
  61.         That means that your computer CAN *NOT* be damaged even if
  62.         the scanner goes electrically "mad". You could even connect
  63.         1000 Volts to the scanner's input, the output on the computer
  64.         side would still be held at a standard low voltage!
  65.  
  66.  
  67.  
  68. W H A T ' S   T H E   G O O D   T H I N G   A B O U T   T H I S
  69. D T M F   S C A N N E R ?
  70. ---------------------------------------------------------------
  71.  
  72. Some people use sound cards (like SoundBlaster) to scan digits
  73. dialed on a phone line. The DTMF scanner can be more usefull
  74. cuz it's a *small* device that u can carry in ur pocket :) :) :)
  75.  
  76. It uses low-cost components: the whole thing costs less than $20.
  77.  
  78.  
  79.  
  80.  
  81. T H E   C I R C U I T   D I A G R A M :
  82. ---------------------------------------
  83.  
  84. UUencoded graphic file (DTMF.BMP):
  85.  
  86. [ Section: 1/1  File: dtmf.zip  Encoder: Wincode v1.4 ]
  87. Original Input File Size: 11647
  88. begin 644 dtmf.zip
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  249. MC>F&$;^]T(#;3&K]_L-0M9T&MK3*U'SCDJ_2[<N)\R64K1TR:'LZ+<!OZ?>G
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  268. MF!Z>\R7C1,ELI^JZ3-==P-4"O3XY<DMZI!<0M=F6?!4PO6G:2`+3ZH!)>2]3
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  273. M2)[>LST-ZKDR&S[1GNYEZN>DS5/+2TT;$?4_F9^P?\U.8"NW+]&7!--X*F]Q
  274.  
  275. MYB_\\J@V'W7QX`V9YG#!M#V/"*E2#%K!8%5.$4R'G)<"4PA,P11,(3`%4S"%
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  278.  
  279. MV4>U6[Q1>_K+<F*FW-[OD_@`?K+Q?!/3?;L#CM3]_RNO9,IK=5][IZ8ZMS-E
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  281. M3=)P9<M4GLST'\E+F=(*TVWW8#-*,"15P)3IN4S5OY07,8TZCE*)74P?=DJ^
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  289. M>H8O8\K!T3LR9;O0&7A.@9WN[*,&9EIU&]N8MGF6@7]:8*I:?HFK;6A;49%I
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  291. ML+"R=4^BYJLN%A+T%G:J#MGIW41M==^MRN=]%'34Y]_51X%I.??N4::+!:GU
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  324. M*R=1>QJ?M9WI-<)U#"WE*D^US0SF3ZL$J'R/X`@EUCT:TPF:J9RF?8J9IJ9(
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  326. M01:]K4S9E^#PQ/E*%"3S'2!<AWV;'S--&5&A%9PR%ND+E)A*8I<)4_*\38TI
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  330. MI_V)>B2CFIB42DQ7HH;S3\V4`Z9FU9*BSJ/@D4:#(=],:D,U$Y^TQTXCIDG#
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  332. MLY`2M6H+K]S('S/U0[RT5/0F0SOUW;>M]FQ>/,K4MA_K3O4\SVJ&3AP,(Z9?
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  346. M6S!-QU%G9LK&!"M,76?$2:RD2IGJYB.(P7@3IKY?C+O4?9.P3S#4VJY/9Y"<
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  362. MD[Y80KIBW5<^N4QAW9(#ILDX:"7B[!YV6FY/[<M<6V.C;.Z^O6^WG1[M./EZ
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  368. M;9X/T%X32=B>JE<Q_;N?R#C#.7)+>J07$&UBR4V?2R?]DU\0J+/>_Z%`$`1!
  369. M$`1!$`1!$`1!$`1!$`1!$`1!$'0!J?M)WEKJ?I*WUBMBBEY<,^6M!:9@"J9@
  370. M"J8OOP.;O64Z"RG9/\Z1()N;1P?JVV/ZA[(OL=L4;8LKFZQ8=\7*_2JF7[8G
  371. MFJUDRB:.9C*I0*2#SLV4'*60J7E1/W%H=)9M^\-S\\5-6<?7,S6O3A]&\-'<
  372. MANGT]V%1(5.E@_3UCC1B_T,\4W.4O`W;EV>F8I/3J.!U\XS]UQG=C:DX$),U
  373. MEIG*S%3*3"5B*O=CJCPVNV=L9JK\CSDUKSNJE-MF6V>JE#W'/Y8.NA131XS<
  374. M14GO_?!,+9IF.V6AX#G;K8_W8BI3-^0MS_;N<Y-*V^H^.VMW3/4SJN:4NP%3
  375. MVT<M,EWMHQQ3OB%3-9&5S)=RL#73R"!S7RIAZATK[TM%%GX#GU]/GCFFRNUO
  376. M)%/OO1D'/K]+0&%]?I=7UQ%4K-R9`4)[?;H14XQ-P11,P11,P11K?%@WO3U3
  377. MJ*_^];L"]<Z%]&\%ZJQ_]^L"==;/?TV@SOK,;PG4N^Z_(U#O7$@L4&?]=?A2
  378. MW?7=W_O_4$L!`A0`%`````@`8`!T(*%-`D`-+0``)DL%``@````````````@
  379. E`````````$14348N0DU04$L%!@`````!``$`-@```#,M````````
  380. `
  381. end
  382. [ Section: 1/1  File: dtmf.zip  Encoder: Wincode v1.4 ]
  383.  
  384. How does it work?
  385.  
  386. A digit dialed on a phone line is a simple sound containing
  387. two special frequencies:
  388.         1 --->  697Hz & 1209Hz
  389.         2       697     1336
  390.         3       697     1477
  391.  
  392.         4       770     1209
  393.         5       770     1336
  394.         6       770     1477
  395.  
  396.         7       852     1209
  397.         8       852     1336
  398.         9       852     1477
  399.  
  400.         *       941     1209
  401.         0       941     1336
  402.         #       941     1477
  403.  
  404. The circuit used here uses 5 cells with a NE567 device and a
  405. LED in each cell. Each cell will be adjusted for detecting one
  406. of the special frequencies above in the sound carried on the phone
  407. line. When the cell detects the frequency it LIGHTS THE LED.
  408.  
  409. The uA741 part: it's here to fix the level of the sound (like an
  410. amplifier) that is sent to the 5 NE567 cells. At first just adjust
  411. the 100K variable resistor at half its way.
  412.  
  413. Use the variable resistors (220K) to fix the frequency detected
  414. on each of the 5 cells:
  415.         cell 1 has to light ONLY IF digits 1 or 2 or 3 are dialed
  416.         cell 2 has to light ONLY IF digits 4 or 5 or 6 are dialed
  417.         cell 3                             7 or 8 or 9
  418.         cell 4                             1 or 4 or 7 or *
  419.         cell 5                             2 or 5 or 8 or 0
  420.  
  421. So cell 1 will detect frequency 697Hz
  422.         2                       770
  423.         3                       852
  424.         4                       1209
  425.         5                       1336
  426.  
  427. You can then know what digit is dialed simply by looking at the
  428. LED or LEDs which are on:
  429.         LED1 & LED4 ---> 697Hz & 1209Hz ---> digit=1
  430.            1      5      697     1336              2
  431.            1             697     1447              3
  432.            2      4      770     1209              4
  433.            2      5      770     1336              5
  434.            2             770     1447              6
  435.            3      4      852     1209              7
  436.            3      5      852     1336              8
  437.            3             852     1447              9
  438.                   4      941     1209              *
  439.                   5      941     1336              0
  440.  
  441. NOTE: if u find that too many LEDs are on then it means that the uA741
  442.       part delivers too powerfull sounds. If u find that too few (or none)
  443.       LEDs are on, then it means that the uA741 part delivers sounds at
  444.       a too low level. All u have to do is fix the 100K variable resistor
  445.       to get a good working sound level delivered to the 5 cells.
  446.  
  447. The outputs OUT1...5: these r used if u want to connect ur scanner to
  448. a computer's centronic interface. When LED1 is on, OUT1 is at the low TTL
  449. level (0V). When LED1 is off, OUT1 is at the high TTL level (+5V). LED2..5
  450. and OUT2..4 work in the same way.
  451.  
  452. If u r using these outputs then u must have D0=+5V so that the "TIL" chips
  453. (these r the opto-isolators) can work. D0 is the Data bit0 output of the
  454. centronics interface, so ur program on the computer must output a "1" on
  455. this pin to take it to +5V.
  456.  
  457.  
  458.  
  459.  
  460. T H E   P R I N T E D   C I R C U I T   B O A R D :
  461. ---------------------------------------------------
  462.  
  463. The PCB construction plans (tracks, pads, components layout) used for
  464. building it on a printed circuit board is contained in a file named
  465. DTMFPCB.ZIP: it contains a high resolution graphic file that you can
  466. print on a laser printer.
  467.  
  468.  
  469.  
  470.  
  471. U S I N G   I T   W I T H   Y O U R   C O M P U T E R :
  472. -------------------------------------------------------
  473.  
  474. If you want to use your computer for reading the digits, u have to
  475. write a little program that reads the 5 Centronics interface inputs
  476. (pins 10,11,12,13 and 15 connected to the scanner circuit).
  477.  
  478. The electrical state of the Centronics inputs are usually at port addr
  479. 379h: the byte read at this addr has bit7=NOT(pin11_of_the_Centronics),
  480. bit6=pin10, bit5=pin12, bit4=pin13, bit3=pin15. All of these 5 pins are
  481. connected to the OUT1..5 of the scanner circuit, so u just have to read
  482. the byte at addr 379h to know which LEDs are on.
  483.  
  484. Reading the byte of the centronics inputs can be done using instructions
  485. like "INPORTB" in C or "BYTE=INP(&H379)" in QBASIC.
  486.  
  487.  
  488. ***************************************************************************
  489.        [ Jojo (Jojo on Brinta BBS / email an617527@anon.penet.fi)]
  490. ***************************************************************************
  491. *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *
  492.