|Hi All ! Can you hook up a standard FAX to a Cell Phone? Yes, you can! I studied the problem and did it! Remember, a FAX operates the old fashion way, via ' shifted tones ' within the telco's wired bandwidth! So how does one do it?|
Its rather simple really; One has to build an interface adaptor from the cell phone 2.5 mm mic/phone jack via a small isolation audio transformer, some coupling capacitors, a small PC board, a T47 telco female jack, some shielded audio cable and a small box to put all of this stuff into. The audio transformer must have three dc isolated but ac coupled equal windings. The FAX couples into the interface box via its two telco coupling lines. Parts at ' Radio Shack ' !
Also, one needs a small 9v battery to ' fool ' the FAX into thinking that its plugged into the telco line! Remember, a FAX circuit works like a wire line telephone, it wants to see the two levels of closed and open key levels of the telco line! Those levels are approximately => 4.8 vdc and 48 vdc ! Open circuit on a telco line is 48 vdc. When the telco is connected and operating on the line, its at 4.8 vdc! So the audio transformer is wired in series with one of the equal impedance windings with a current setting resistor, select the resistor and wire resistance of the winding so that the current is at 10 mA.
The other two windings couple via two capacitors to the audio of the mic via the 2.5 mm ep male plug via one winding and to the other winding via two cacacitors to the small magnetic earphone in the cell phone via the 2.5 mm ep male plug. The capacitors are for potential blocking to protect the cell phone from external potentials. The 2.5 mm plug goes into the earphone/mic jack on the cell phone.
Once all wired up and hooked up and energized, the FAX will couple into the cell phone via the low band audio shift tones that are the basis of operation of the FAX machine! All audio signals in the cell phone via the 2.5 mm ep male plug are converted into digital RF phase shifted quadrature comm signals that are the basis of the comm network ! The resultant interface box works just fine on Verizon's network and they don't seem to mind at all! Whenever a FAX is needed here to either receive or send a FAX to someone whether on land line or digital network, its just hooked up to the cell phone and energized.
A quick dial up via the cell phone, wait for the FAX receive tone, press the send button and the FAX is quickly sent off. Reception of a FAX is just the reverse, have the 2.5mm plug, plugged into the cell phone, when the phone rings, answer, listen for the FAX send initiate tones, press the FAX receive button and it prints right out!
I have been thinking about marketing this on the web but then again, its so easy to design and build and use, Should I Really?! It doesn't seem patentable.
regards, R. E. Adams, Ph.D, physicist...