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I am in need of something that is put on the phone line which directs incoming faxes to the machine. So the machine will receive faxes only. My machine does not have the ability to know if only a fax is being sent. Therefore treats incoming calls as fax only. Meaning when a call is received it is automatically treated as a fax. Whether it is or not.  phone calls only, fax and phone. Or manual. Which is not wanted. Here is the way I would like it set up.

Put the male end in the outlet. Have two female connectors on the other end. With the machine pluged in one female. Which is where the fax tone gets sent. All other tones are sent to the other connector. With the other female connector for normal phone use.

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The fax tone is only the handshaking signal. None of your fax message is on this tone. After this signal is transmitted and both devices have told each other they are connect through these tones, the data is sent. This data is sent on the same line as your voice, so there is quite a bit more to this than just isolating the fax tone to another line. You will need some type of smart circuit to make this happen. A few discrete components will not do it.


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I think I know what you want to do, now. If you can program a micro, you could connect a port line to the phone line through an appropriate transformer and have it listen for the high pitched tone after it gets the ring signal and produces an off-hook voltage on the line. Obviously, there will be no high pitch in a voice call. If it gets the high pitch, turn on the relay for the fax line. The fax will miss the first handshake, but the fax will always repeat the handshake if it does not get a response. After a very short time-out, if the micro does not hear the tone, then relay to the voice line. You will need to also figure out some routine to reset the micro back to a listening stage again. Perhaps with a little more code to determine when the phone is no longer in the off-hook mode.
Does this sound like what you are trying to accomplish?


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