We are testing with an U.S. Robotics 56K Faxmodem connected to COM2 on a small Alpha Server. 

The following steps were taken on the Alpha Server to configure it for Remote Access.

First,  make sure that the COM port device special files had been made correctly in /dev; to check perform the following command:
	file /dev/tty0*
	/dev/tty00:     character special (35/0)
/dev/tty01:     character special (35/1) ACE_SLU #0 terminal #1 modem_control on

If these files do not exist, then they need to be created; to create these files cd to /dev and perform the following command:
	./MAKEDEV ace0	

Ensure that the modem is connected to the correct COM port. 

Add the following string to the /etc/remote file for testing and port speed initialization:
	tty01:dv=/dev/tty01:br#9600:pa=none:

Make certain that the modem is set to allow DTR and Carrier Detect to be controlled by the host and the modem respectively, particularly important when setting up a dialin connection.  Also make sure that autoanswer is enabled for dialin connections.   These can be controlled by either dip switch settings, software registers or through a combination of both.  Elsa modem may differ slightly.

Currently, the DIP switch settings we are using are UUUUUUUD:

1 U DTR Normal / Turns off DTR Override
2 U Verbal results
3 U Suppress result codes
4 U Echo Off-line commands / Displays keyboard commands
5 U Enables Auto Answer on first ring or value in S0
6 U Carrier Detect Normal / Turns off CD Override 
7 U Loads NVRAM defaults 
8 D Smart Mode / Enables AT Command set recognition 

Test the modem connection.  Use the following command:
tip tty01
The host should respond with the string "CONNECTED". At this point you can then issue AT commands to the modem.  

If you don't see commands echoed, then either you are not connecting to the correct port, or echo has been disabled on the modem. While connected via tip, type the command ATE1.  This should enable local command echo.

Now check the modem register values for &C &D and &S.  Some modems will show all of the registers with an ATI4 command.  Other modems require you to display them individually.

The following output is from the ATI4 command on our USR modem:

U.S. Robotics 56K FAX EXT Settings...

   B0  E1  F1  M1  Q1  V1  X4  Y0
   BAUD=9600  PARITY=N  WORDLEN=8
   DIAL=TONE    ON HOOK   CID=0

   &A0  &B1  &C1  &D2  &G0  &H1  &I0  &K1
   &M4  &N0  &P1  &R2  &S1  &T5  &U0  &Y1

   S00=001  S01=000  S02=043  S03=013  S04=010  S05=008  S06=004
   S07=060  S08=002  S09=006  S10=014  S11=070  S12=050  S13=000
   S15=000  S16=000  S18=000  S19=000  S21=010  S22=017  S23=019
   S25=005  S27=000  S28=008  S29=020  S30=000  S31=128  S32=002
   S33=000  S34=000  S35=000  S36=014  S38=000  S39=000  S40=001
   S41=000  S42=000

   LAST DIALED #:

AT$ should provide help and a command quick reference for all values.

The following commands were used to change values on our test modem:
AT&D2	DTE Controls DTR
AT&C1	Modem Controls CD
AT&S1	Modem Controls DSR
AT&H1	CTS
ATF1	No Online Echo
AT&A0	Disable /ARQ Result Codes Bingo!!! This one did the trick.

In most cases &C and &D will be correct by default, but they should be set to allow "Normal" CD and DTR operation respectively.

The register &S controls DSR and may need to be changed to allow the modem to control DSR. If so, then change the value.

When completed, save the registers to allow them to survive a power cycle of the modem.  This was done with   or AT&W0, but some modems may require a different command.

After saving the modem configuration, exit tip, by typing tilde., “~.”

For a dialin connection, it is necessary to have a getty process running against the tty device.  This process is started by the init process and so the following line must be added to the /etc/inittab file:
	/etc/inittab:	tty01:23:respawn:/usr/sbin/getty /dev/tty01 M9600 vt100

Once the changes to /etc/inittab have been made, issue the command:
init q
This command will cause the init process to reread the inittab file. This process should then spawn the getty which will start the login process when an interrupt is seen from the modem attached to the port.

Note
We will probably need to configure PPP or SLIP at some point, in the very near future and I will send some additional information regarding this configuration after I research it a bit more.