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Text File  |  1992-11-09  |  2.0 KB  |  59 lines
  1. Newsgroups: sci.electronics
  2. Path: sparky!uunet!email!eiaut2.tuwien.ac.at!ch
  3. From: ch@eiaut2.tuwien.ac.at (Christian Kral)
  4. Subject: Re: Phone line monitor
  5. Message-ID: <1992Nov9.123237.27633@email.tuwien.ac.at>
  6. Sender: news@email.tuwien.ac.at
  7. Nntp-Posting-Host: eiaut2.tuwien.ac.at
  8. Organization: Technical University Vienna, AUSTRIA
  9. References: <16894F0EE.X1FT@VM1.CC.UAKRON.EDU> <7380090@hpnmdla.sr.hp.com>
  10. Date: Mon, 9 Nov 1992 12:32:37 GMT
  11. Lines: 46
  12.  
  13. Here are my improvements. Easy, cheap and powerfull:
  14.  
  15. Add an rectifier to the input lines. This prevents from any damages due
  16. to wrong connection. Just connect the AC-inputs to the line and
  17. "+"-output to "Phone+" the "-"-output to "Phone-". Add an simple Diode
  18. from pin 5 in the picture to the +9V point facing the battery (the
  19. marker ring should point at the bat.). This will help against CMOS
  20. overload problems.
  21.  
  22.                                                             +9V
  23.                                                              |
  24. Phone+   -----+                                              |+
  25.               |                                             LED
  26.               R 2.7Mohm                                      |-
  27.               |                                              |
  28.               |                                              R 680 ohms
  29.               |         5 |\ 4          3 |\ 2               |
  30.               +-----------| >o------+-----| >o---------------+
  31.               |           |/ 4049   |     |/ 4049            |
  32.               |                     |                        |
  33.               |                     |                        |
  34.               R 0.56Mohm            |  14 |\ 15              |
  35.               |                     +-----| >o---------------+
  36. Phone-  ------+                           |/ 4049
  37.               |
  38.               |
  39.              GND
  40.  
  41.  
  42. By the way.....
  43.  
  44. In his article Roger writes:
  45.  
  46. >
  47. > Voltage going into pin 4 of 4049 is:
  48. >
  49.  
  50. this should mean:
  51.  
  52. Voltage going into pin 5 of 4049 is:
  53.  
  54. That's it!
  55.  
  56. Christian.
  57.  
  58.  
  59.