These settings seem to work. The general idea is that the modem on the machine under test must be set up so that RTS/CTS (hardware) flow control is off and xon/xoff (software) flow control is on (assuming that the modem supports flow control, which is not the case for most older 2400 baud modems). If your modem is not listed below, you need to look up in the manual how to: Ignore DTR Autoanswer on first ring Use XON/XOFF Flow control It is usually a good idea to type AT&F to reset to factory default settings before setting other parameters. When you are all done with the debugging, use AT&F again to clear out the debug-specific settings. Gateway Telepath: US Robotics (including Gateway labeled): switches vary from model to model, but there is normally a reference card underneath the modem. Switch numbers are given for the Sportster 14,400 Data Terminal Ready (DTR) Operations (switch 1 down): DTR always ON Auto Answer (switch 5 up): Modem answers on first ring. AT commands: AT&h2&i1Q2&r1&w For Telepath, add &d0s0=1 before the &w For HST Dual Standard, add B0 before the &w you may need to set at&n6 if you have a modem capable of 14.4 kbs, as this connection seems funny with many modems. &n6 limits the user to 9600 bps connections, only. &n3 sets it to 2400 baud. Telepath modems: Telebit modems (except Trailblazers T1000/T1500/T2000/T18PC): No switches AT commands: AT&d0s0=1s51=4s58=3&w IBM model 7855-10: No switches From menu, first setup menu, choose AT instead of v.25bis command set Note: these modems seem to lose their settings, despite the AT&w command. Also, I have at one site had to have the serial cable removed from the com port once the system hung before the modem would answer. In this case, just let the modem answer and re-attach the cable. AT commands: AT\m12\r1&d0s0=1&w Multitech v.32: modem has two dip switches, one with 4 and one with 8 switches. On the eight pole switch, switch 1 is down (dtr force on), switch 5 is up (enable autoanswer), switch 7 down (RTS on). On the four pole switch, switch 1 down (CTS on), 3 up (Hayes mode) AT commands: AT&e5&w Multitech Multimodem 2: On the eight pole switch, switch 1 is down (dtr force on), switch 5 is up (enable autoanswer), switch 7 down (RTS on), switch 11 is up (AT response), switch 12 is down (Async mode), switches 13 - 14 are up (force 9600), switch 15 is up (CD & DS normal) AT commands: AT&e5&w Hayes Optima and V-Series, Practical Peripherals Boca, Zoom, and many others: No switches AT commands: AT&k4&d0s0=1&w AT&T Paradyne No switches AT commands: AT\Q1\X1&d0s0=1&w0 Prometheus Promodem Ultima No switches AT commands: AT*f2&d0s0=1&w Intel SatisFAXtion 14.4 No switches AT commands: at\q1&d0s0=1 Motorola UDS v.3227 No switches AT commands: AT\q1\j0&d0s0=1&w Spartan or Microcom Deskport No switches AT commands: AT\Q1\X1&d0s0=1&w Hayes Smartmodem 1200 or 2400 or 9600: Note that the older Hayes Smartmodem 9600 (NOT V-Series, Optima, etc.) used their own proprietary 9600 baud modulation and are only usable at 2400 baud with most modems available at IBM. No switches AT commands: AT&d0s0=1&w Special note for Hayes Smartmodems: in order to hang up and leave a system running, the customer at the MUT must briefly remove the phone line from the modem. If the remote system just hangs up its modem, the MUT's Hayes will often generate a ctrl-c that will interrupt the remote kernel.