Written By: Jerry Mills
How to connect a Hayes compatible Modem to a DTC on HP3000 MPE/XL
Step One - Set up the modem with a terminal connected directly to the modem. A 40242M cable (straight through cable) or a PC straight through 25 pin to 25 pin cable. Configure the terminal for the same BAUD rate and CHARACTER FORMAT the DTC port will be operating at. THIS IS VERY IMPORTANT! Hayes compatible modems sense the BAUD rate speed and character format at which they will be working from the ASCII characters ‘AT’ which we will be using to initialize the modem. Once we save the commands with ‘AT&W0’ the modem will be permanently configured for that BAUD rate and character format. That means if the power is cycled (i.e. on/off) the modem will operate at the last saved ‘AT&W0’ command.
NOTE: DTC serial ports do not send initialization strings to a connected modem like PC’s do.
AT&F <set factory defaults>
Next disconnect the terminal and connect the modem to your DTC using a 92219Q or 40233A Cable.
AT&C1 <tracks presence of carrier>
AT&S1 <tracks presence of DSR>
AT&D2 <normal function of DTR when line drops>
ATS0=1 <set auto answer to one ring>
AT&Q0 <asynchronous mode> (9600 Baud modem only)
AT&K0 <local flow-control disabled>
ATQ1 <modem doesn't return result codes>
ATE0 <disable character echo in command state>
AT&W0 <save parameters in user profile 0>
AT&V displays all settings
The 92219Q cable uses pin 23 which is know to cause problems with the DTC16iX/MX/TN dtcs. So if making a cable just leave off the pin 23 connection. The 40233A cable doesn't use pin 23 else everything is the same.
On the system run nmmgr and configure the port on the DTC for a modem profile (usually TR10U96). The following is the setting for that profile:
Terminal type 
Line speed [9600 ]
Record width [80 ]
Modem type  (0 - none, 1 - US, 2 - European)
Speed/Parity Sensing? [Y] Allow :HELLO logon? [Y]
Reset HP terminal? [N] NLIO device? [N]
Make sure you Validate the changes in nmmgr, Cross-Validate them in SYSGEN with rdcc, shutdown the system and do a Start Norecovery, and cycle power on all the DTCs after the SNR.