You are not going to get anywhere near 56k using only analog lines. 56k modems relied on one side (usually the ISP) having access to digital lines. This allowed the modem to sync with the phone system clock and the A/D conversion at the far end. Without this syncronization I believe the best that could be done was 28.8k. But that was with dedicated hardware.
Is there a reason that you can't just plug in a couple of modems to the same lines? If you are making a call then sending a short burst of data, then hanging up, a slower modem (2400) or less might be faster. The high speed modems took considerable amount of time negotiating speed when connecting while your slow modem could connect send a bit of data and hangup in the same period. Another low speed solution might be DTMF asterisk and the ATAs know how to handle that and it sends 4 bits at a time. ----- Original Message ----- From: Bruce N [mailto:[email protected]] Sent: Saturday, December 10, 2011 05:13 PM To: [email protected] <[email protected]> Subject: [on-asterisk] What Modulation/Demodulation add-ons for various frequencies exist for Asterisk? 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.
