David Nebenzahl wrote:

On 1/2/2010 4:37 PM Adrian C spake thus:

David Nebenzahl wrote:

Everything seems configured correctly: I've set the speed at both ends
to 56K and disabled waiting for dial tone.

So what am I doing wrong here?

The maximun speed you should set for is 33.6 kbps analogue.

Above that, the communication relies on connection to an ISP's modem
rack port supporting digital network signalling, something that is
missing on your back-to-back attempt.

Thanks. I bumped the speed down to 19,200 (I think*); the sounds were
different, but still no success.

Couple questions:

1. Are the sounds one hears on the RX side those of the sending modem,
the RX one or both?

2. * Hard to tell with HyperTerminal what speed is actually being used.
I configured to modem to use a maximum speed of 19,200, but HT still
said "112xxx" (forget the exact #s) until I went and re-configured the
modem, at which time it then said 19200.

This really should work.


Both modems are set for the same mode. One has to be switched so you
have 'Answer' & 'Originate' modes.

http://hw-server.com/docs/atcommset.html lists some of the commands
in the old Hayes compatible series.

Some early terminal programs set up the modem for you. Some people
just used a freeware 'Bulletin Board' program to get around the problem.

As far as the DC voltage, some modems don't have the telephone line
transformer. They use a set of diodes instead. These need enough
voltage to forward bias them, but it has to be current limited to a few
mA to prevent damage. The DC voltage on a phone line is listed as -48
volts nominal and referenced to ground, but if you were close to the
older type central office it was in the low to mid 50 volt range.

You can also use 'Direct Cable Connection' for serial or parallel
connection of two computers. The cables are easy to make, and a lot
faster than using modems.

Open 'help' in the windows start menu and type cable into the search
box for information. I used to use the parallel port version in Dos and
Win 3.1 days to install software on some computers. That way I didn't
have to install, then remove a CD-ROM drive to install the OS and
drivers. It was also useful to run OEM drive software to repair screwed
up drives after people tried to do Win 95 installs and messed up the low
level format.

Another approach is an external drive enclosure with a USB
interface. Pull the one drive and slave it to the other computer.


The simplest though, is a pair of $10 network cards and a ethernet
cable.

--
Greed is the root of all eBay.