How to use two OBI110 as a Local Area Network Intercom
QBZappy:
Pinky,
Cool idea of writing tag words in your post in small sized font. I never saw this before. For a moment there I though that you were writing some sort of subliminal message at the bottom. It might be useful for readers who want to tag hard to find threads as well.
Pinky:
They are actually 9600 baud modems. I recently had great success using a pair of VOIP boxes (intended for the two way radio industry) emulating a 4 wire lease line that I connected the 9600 baud modems through. Ended up being a stable connection, though I think part of the success was the fact it was on a private IP network. The modems I used for that setup are capable of dialup, 2 wire lease and 4 wire lease.
I was thinking if I could get away with using 2 wire lease line modems, they would be more plentiful and cheap used plus I could use a relatively cheap ATA (compared to the 4 wire VOIP boxes).
Is it too much to ask for out of the OBIs to do 9600 baud even OBI to OBI direct with no VOIP provider?
BTW- QB, I saw the small font technique somewhere else a while back before and thought it useful.
Shale:
Quote from: Pinky on July 30, 2013, 01:57:25 am
Is it too much to ask for out of the OBIs to do 9600 baud even OBI to OBI direct with no VOIP provider?
Actually I don't know. I have never tried anything like that. I am probably over-pessimistic. I hope your ethernet path is low on jitter.
ianobi:
The general advice for faxing over voip is to lower speeds to 9600 Baud and ensure that only uncompressed codecs are used such as G711. OBi devices do use G711U and G711A codecs, so that side should be ok. You would probably have to go peer to peer, not via a voip provider, to ensure that signals don't get compressed by the voip provider.
I believe that there are some differences between how faxes and straight modems work, but you need someone more expert than me to talk about that! All I know is they both push data down telephone lines.
If your two modems can seize a telephone line and auto-answer when they receive ringing, then the above azrobert config should work. You might need to experiment with the config to eliminate connection delays. Also note, that the original question concerned two OBi devices on the same subnet. If you try this project out, then it would be easiest to set it up on the same subnet first for easy fault finding.
Anyhow, looks like an interesting project. We would all like to hear about it if you give it a try - we might even help :)
Pinky:
Sounds good Ian and Shale-
I've got a couple more modems on the way to play with on the bench so I'll give it a shot. I've got two OBIs already so I'll try out this configuration and see what's what.
I understand about the jitter- I was concerned about this with my 4 wire VOIP box setup. That particular install is on a low latency private IP network which has a very consistent 10ms ping . Knowing the buffer time of the boxes, the modems, and the ping, the total latency of the synchronous serial data is about 125ms.
Is there a buffer adjustment on the OBI I can set?
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