At 10:37 18/08/99 +1000, you wrote: >Hi Duilio > >I can't read your schematic. I have never had any luck reading ascii >schematics I receive as email. However I have an off hook detect circuit >that I think is simpler then what you have suggested here just going by the >number of components. Mine uses an opto coupler and does ring detect among >other things so you would have to sort out the bits you need from the other >stuff. If you are interested I can send you a schematic privately as an >Orcad file or I could paste it into a Word document or something. > >Steve > Judging from his other comments this will be too complex, or he has seen that, or will not be a single chip soultion But it would be nice if people would place all thier requirements in one go rather than letting out little pieces of it here and there. Like the inevitable carrot for the horse, removed before he gets to it, yet another hurdle is placed in the way of those whom whish to help. I am not having a good day, sigh, I think I need another job, anyone need me in Victoria? Currently studding my Masters. (No doubt that my thesus will be flamed too!) Dennis >-----Original Message----- >From: Duilio Foschi >To: PICLIST@MITVMA.MIT.EDU >Date: Wednesday, August 18, 1999 8:02 AM >Subject: help re a telephone circuit > > >>I want to build a test circuit that will enable me to detect when a phone >>goes off-hook and detect the DTMF tones thru a modem. >> >>I was told to use the following circuit: >> >>(please enlarge your screen to display it) >> >> phone >> >> | | >> | | >> | >>+--------------o-----------o--------------------------------------------o-- >- >>----------------o >> | | | >>| | >> | | | >>| | >> | +-+ | >>+-+ | >> | | | R=100K | >>| | | >> | | | | >>| |R=1K | >> | +-+ | >>+-+ | >> | | | >>| | >> | R=1K | | >>| | >> | +-----+ | +|\ | 741 1N4148 1N4148 >>/ | >> o---| |----o---------------| \|+ |\| |\| +-----+ >>|/ ----- 12V >> | +-----+ | | | \-----------| |-------| |------| >>|-----| 2N2222A --- >> | | | | / |/| |/| +-----+ >>| | >> | | O--------| /|- R=10K >>> | >> | | | -|/ | >>\ | >> | + + | | >>o---o hook | >> | R=560| | | | >>| detect | >> | ohm | | +-+ | >>+-+ | >> | | | | | R=10K | >>| |R=560ohm | >> | +-+ | | | >>| | | >> | | +-+ | >>+-+ | >> | | | | >>| | >> | >>+-------o------o-----------o--------------------------------------------o-- >- >>----------------o >> | | >> | | >> >> modem >> >> >> I know very little about telephone circuits: >> >> 1. will it work ? >> 2. can I lower the voltage, say to 9V ? >> 3. is there a better circuit ? >> >> >> Thank you >> >> Duilio Foschi >> > >