Using Speakers + Mic attached to a modem

[FunkyChicken]

Hi guys,

I was wondering if it is possible to attach to my laptop modem, a speaker for the send and a mic for the recieve, i could then attached the mic to the earpiece of the telephone and the speaker to the voice part of the telephone (have i explained this well enough?)

then in thery i could use any public payphone to quickly establish an internet connection and download my emails. Is this at all possible?

How would i wire this into my laptop?

[FunkyChicken]

P.s. i have searched quite a bit in google but i keep coming up with hopspots being added into payphones.

[Thorn]

What you're describing is an acoustic modem. It's very old technology.

[astcell]

Acoustic modems are fun. Ira will have some no doubt, but then you have to find a phone that will fit it.

[TheCotMan]

Acoustic modems are fun. Ira will have some no doubt, but then you have to find a phone that will fit it.

They even show one in the movie WarGames. In the movie, it is a solid unit. I've seen some on ebay that were not solid units; they were separated into the speaker and mic and could be attached separately. (Most will probably use DB9/DB25 RS232 type Serial connectors.)

However, use of a public phone for purposes like this can be expensive (if you pay for you calls.) Even local calls may cost $0.50 and only last 3 minutes. Long distance rates can be 500% over home rates (or more.) Use of a prepaid calling card is a great cost saver. (Some go down to $0.05 per minute.)

WiFi Cafe or public library would probably be cheaper for 1 hour, be more reliable, and give faster speeds.

[astcell]

What is the max speed that acoustics can give? 4800 baud? I mean what is the theoretical limit due to the air transfer, not the speed of modems back when acoutical modems were out (300 baud or so).

[noid]

I've seen 9600 baud acoustic coupler connections. Its scary, but there are still companies making them today.

[FunkyChicken]

thanks for the help guys.

all i will use it for is to collect my emails when im out camping in the middle of nowhere, in the uk we have an area code which charges for a local call regardless of where u phone from. this is what most ISPs use for their dial-up number.

there are also a few small freefone numbers in which i wouldn't have to pay at all, they must make their money from all the advetising, everytime you connect you have to go through their html connection page with loads of adverts on.

once again cheers for the help, im gonna go on a little reading mission now and see about making my own.

P.s. im currently on a 2MB connection (fairly fast for a home user in the uk), it will be a kick in the teeth trying to surf at a slow speed

P.p.s. i did try using my cantenna from the campsite but i couldn't pick up a thing for a quick wifi link

[Thorn]

In the August 1980 issue of Byte, the Ciarcia's Circuit Cellar column had an article "A Build-It-Yourself Modem for Under $50" (It was reprinted in the Byte Publication book Ciarcia's Circuit Cellar, Volume III.) You may be able to track down a copy of one or the other.

The article was a how to for constructing an acoustic modem. While the circuits involved are obviously long outdated (it was 300 baud max) , the physcal contruction of the acoustic coupler would still apply. Ciarcia designed a split acoustic coupler with closed cell foam that would fit variety of telephone handsets. Also, the article gives a nice little primer on Frequency Shift-Keyed (FSK) modulation, which is the basis for audio communications of this type.



There's no tech, like old tech.

Or maybe there's no techies, like old techies...

[highwizard]

There's no tech, like old tech.

Or maybe there's no techies, like old techies...

Thorn, since we're being totally offtopic - How's the WarSpying Project going?

[renderman]

There was a txt file years ago about how to mod a normal phone into a acoustic coupler just by splicing a 9v battery into one of the lines. Combine that with proper acoustic couple 'cups' for the mic/speakers and you could do it yourself. I know Uncle Ira was selling the cup parts at about DC7

I've actually seen homebrew units like this at 14.4 and 19.2. The quality of the speaker/mic and blocking external noise are key things to watch.

[Thorn]

Thorn, since we're being totally offtopic - How's the WarSpying Project going?

It comes and goes depending on my time to work on it. A month ago I was able to do some good research on various capture routines and how to improve the really crappy design of v0.1. But I haven't touched it since then, due to being busy with some new clients.

It's funny though, you're the second person to ask about it in three days. Maybe I should make some time to work on it some more.

[FunkyChicken]

Hows the WarSpying Project going thorn?

thats the 3rd now

[Thorn]

Alright! Alright! I'll get back to it! Jeez...

Hey, shouldn't you be working on an acoustic modem or something?

[astcell]

I smell another contest.

Capture the Flag, but no hardware or software used can be newer than 1994.