Bruce,
Sounds like your best route would be to look at T.38, since a fax is
just a tif image converted/encoded so it can be sent over a fancy modem
and decoded and reconstructed. Depending on the size of your data packet
, if it is small you could use the fax negotiation and send the data in
the fax header or if larger, you could encapsulate your data in a tiff
file. Then transmit , decode then extract your encapsulated data.
Just a thought!
Mike
On 12/10/2011 5:13 PM, Bruce N wrote:
Hi everyone,
I have a situation where there is a PSTN line but there is no 56k Modem;
However there is a Linksys ATA with an FXO port attached to PSTN line and
registered to Asterisk. I want to stream "data" back and forth. No audio.
I understand that is what a 56k modem best does in case of a PSTN analogue
line. I want to know if there is any method, algorithm (like using various
pitch sounds to send data) that I can take advantage of with or WITHOUT
using Asterisk? Currently, I am looking to send alpha-numeric in
30-50 characters but later on, it can get larger so error correction, error
detection (maybe using a hash digest), and as fast data-transfer as
possible (close to 56k) is ideal. I am assuming that 56k modems are the
fastest possible over analogue lines (since they have patented algorithms
and chips specifically built for this purpose)?!
Currently in Asterisk 1.8x there is a morsecode() application which is
really cool but of course it's very slow. Also, there is no Morse code
reader for Asterisk (I could be wrong; please correct me if so). Or a very
basic thing I can do is to use DTMF and assign each letter a number and
transmit/decode on the Asterisk side but it will be really slow for my
purpose. So, something like that should do the job but since this is to be
machine automated I am sure it can be much faster using various pitch
sounds in much smaller intervals per code. Another example of this is some
programs that exist for amateur radio operators where a radio along with
GPS can be used to track location of a car.
Any input, however technically in-depth, is much appreciated.
--
Mike Ashton
CTO
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