> > For a connection, i have to type ATA on B modem, and ATX3 on A modem. > >The problem is that the machine that i will connect on modem B only wait > >for a CONNECTION status, nothing more, the machine can't send a ATA > >command to MODEM B. > > The modems need to see a little line voltage (off hook voltage) to work > correctly. This is usually from 3 to 9v. To achieve this, connect power > supply that provides a clean DC output, or better yet, battery in parallel > with the phone line between the two modems. The north american standard is > a > red wire (ring/B) for -, and a green wire (tip/A) for +. > > | < Connect to negative terminal of PS/Battery > ---------+ | +-------------+ > modem A |Red -------+-----| modem B | > |Green -------+---| | > ---------+ | +-------------+ > | < Connect to positive terminal of PS/Battery > > The power supply MUST be well filtered & regulated. Any power supply hum > on > the telephone line will probably ruin any hopes of high speed data > transmission. > > This surely can not be correct, the presence of a nice low impedance battery or PSU would effectively short the lines for any signal, making comms impossible. I thought the the supply was effectively in SERIES with the line? Mike Rigby-Jones