Thanks Tracy! Nice to have very detailed info on the mods, etc. And I like the way you modified the 485 to run std. 5v TTL RS232. Elegant. I looked on eBay and saw these modems running for around $8 each, give or take, so you got a good deal! Will this plan work with any of the Teleport line (there's Gold, Bronze, Fax, etc)? And given the small data sizes I'll need to send, 2400 is fine. Even with the far-far-far top end of data I might have to send eventually, it would still go in 4 seconds....
I'm finding so much good stuff on old modem tech it's starting to look interesting again, now that my mind is thinking of other possibilities. A lot of my projects would benefit from two way communication, but clients don't have internet access available at the box's location, and they don't want to spend the $$$ for a cell contract to cover the sim card style of communication... but it's cheap and easy to run an analog phone line out to the box. Possibilities are starting to bloom in my brain like a spring garden after a rain shower!
1. Majority of USB modems are so called "host based" modems, in hardware they only present interface to line, all processing is done via software, so you can't run it via prop, bs2 or whatsoever. Go for models with COM port.
2. You won't be getting 56k uplink speeds with two V90/V92 modems, because protocol is asymetrical, so 33k is your best theoretical. In practice, 21.6k will be very good luck.
Modems are certainly NOT obsolete, just ignored. Just consider how many of us have a land line installed that is rarely used while we communicate by cellular line.
I suppose the only complexity is having switching if one calls in via voice. The 'usual' solution is to pick up after so many rings and attempt modem communication. ... something like 10 or 12 rings. Calling out is not really an issue.
The cheap ones were Bronze, 2400 baud. I had a Global Village Teleport Gold Fax-modem too, (Imagine, 9600 baud!).
When two modems start to connect, they have to negotiate the speed and protocols. Things go much faster if you can limit them via AT commands in advance what to try.
It can be a bit of hassle to get it going, but really no more than cellular. It is the way things used to be and is very stable technology. Cellular, you never know what is going to change at your local cell tower. And now the big carriers are dropping GPRS in favor of HPSA.
Comments
I'm finding so much good stuff on old modem tech it's starting to look interesting again, now that my mind is thinking of other possibilities. A lot of my projects would benefit from two way communication, but clients don't have internet access available at the box's location, and they don't want to spend the $$$ for a cell contract to cover the sim card style of communication... but it's cheap and easy to run an analog phone line out to the box. Possibilities are starting to bloom in my brain like a spring garden after a rain shower!
Dave
1. Majority of USB modems are so called "host based" modems, in hardware they only present interface to line, all processing is done via software, so you can't run it via prop, bs2 or whatsoever. Go for models with COM port.
2. You won't be getting 56k uplink speeds with two V90/V92 modems, because protocol is asymetrical, so 33k is your best theoretical. In practice, 21.6k will be very good luck.
I suppose the only complexity is having switching if one calls in via voice. The 'usual' solution is to pick up after so many rings and attempt modem communication. ... something like 10 or 12 rings. Calling out is not really an issue.
When two modems start to connect, they have to negotiate the speed and protocols. Things go much faster if you can limit them via AT commands in advance what to try.
It can be a bit of hassle to get it going, but really no more than cellular. It is the way things used to be and is very stable technology. Cellular, you never know what is going to change at your local cell tower. And now the big carriers are dropping GPRS in favor of HPSA.