Description of a suprisingly simple hardware modification to the OSBORNE-1 to supply software controlled Data Terminal Ready to a modem connected to the RS-232 Serial Port. It is assumed that those interested in applying the mod knows how to field strip the OS-1 and remove the motherboard and also has an understanding of how to tack solder connections to integrated circuits. If you don't have these basic skills, try and find a helper you trust that has the knowledge and can guide you. ...................... After removing motherboard, locate R-29 (about 2 inches or so behind RS-232 connector). It can be further identified by a land running from the resistor to pin 6 of the RS-232 connector. Remove R-29. Cut and dress approximately 2 inch wire. Tack solder one end of the wire to pin 5 of the ACIA and the other end to the hole NEAREST, repeat NEAREST, the RS-232 connector where R-29 was removed. DO NOT use the hole closest to the ACIA as that is +5 volts. Thats all there is to it. This will give DTR on pins 5,6 & 8 of the RS-232 connector as long as RTS is high (which it is when you are using the RS-232 port). If you were using +5 volts from any of these pins for anything else (can't think of what), you're out of luck on one or the other as the Osborne schematics do not agree with the motherboard. If you need +5 volts for another use (??), an alternative is to leave R-29 in, cut the land on the reverse side of the motherboard between pins 5 & 6, or 6 & 8, and jumper the ACIA to pin 5 or 8 of the RS-232 connector. Then configure your modem cable to supply DTR according to the method selected. ..................... Programming considerations: Write 6xH (x is don't care) to the MODEM Status port (2A00H) to drop DTR to the modem. Then write 56H or 55H to set 300 or 1200 baud again. You may have to include a routine to reset your modem after setting DTR again as I had trouble with my Prometheus getting the baud rate dinged up, but that is a known problem with some smart modems. The routines to send ATZ to reset Hayes compatible modems can be borrowed from the Smartmodem overlays by copying the SMSEND routine. ................... Don't know if you need this mod, but my BYE and MEX certainly worked MUCH better after I made it. I have to admit, I studied the mod a long time before attempting it since it was so simple I wondered why OCC did not incorporate DTR to begin with. Good luck and happy hacking. Larry G. Bell