I have a Mitel EL 200 that I am trying to dial into the maintenance port with a U.S. Robotice 56k Modem. Switch settings are 1 3 4 8 down. Straight thru 9 pin cable with a converter from 9 pin to db25 at the modem. The modem will answer and connect, but I am unable to talk to the Mitel. If I am on site, I can use hyper terminal and the same cable, hook up to the maintenance port and I can talk to the switch just fine. Any help would be appreciated.

Switches 1 and 4 should be down, the rest of them up.

And you need a NULL Modem cable from the modem to the system!
I use 4 and 8 down and the rest up once I have set up the serial port speed at 9600 with the command AT&B1 and AT&W1. (HyperTerminal should be talking to the modem at 9600.)

this is how I programmed mine:

SX-200 ELX
US Robotics Modem Settings
Dip Switch settings 1, 2, 4, 6, 7, all up
0=Zero
1) Type at&f enter
2) Type atm0&n6&b1 enter
3) Type atq1e0&w enter
4) Turn modem off
Put switches 1,4 Down all others up

and then connect with null modem cable

Here is another:
WARNING: ALL “AT” COMMANDS HAVE 0’S (ZEROES) NOT O’S(OH’S) IN THEM!!!
Step 1: Verify your USR 33.6 or 56K V.92 modem register bits are setup as follows. To determine
the modem's current settings, connect the modem to a laptop at 9600 8N1 Flow Control = none
with a null modem cable (pinouts are below). Before powering on the modem, set dip switches
1,3 and 8 down, the rest of them up.
Type ATI4, then press your enter key. After pressing your enter key, the modem’s current
settings will be displayed. Depending on which modem you are using you will want to set them up
according to the settings listed below for that modem type.
USRobotics Sportster 33600 Fax Settings...
B0 E1 F1 M1 Q0 V1 X1 Y0
BAUD=9600 PARITY=N WORDLEN=8
DIAL=TONE ON HOOK
&A1 &B0 &C1 &D0 &G0 &H0 &I0 &K1 &M4 &N6
&P0 &R1 &S0 &T5 &U0 &Y1
S00=001 S01=000 S02=043 S03=013 S04=010 S05=008 S06=002
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 S36=014 S38=000 S39=000 S41=000
USR 56K V.92 FAX modem settings…
(BOLD LETTERS IN REGISTERS ARE USED BELOW IN THE EXAMPLE IN STEP 2.)
B0 E1 F1 M1 Q0 V1 X1 Y0
BAUD=9600 PARITY=N WORDLEN=8
DIAL=TONE ON HOOK CID=0
&A1 &B0 &C1 &D0 &G0 &H0 &I0 &K1
&M4 &N6 &P0 &R1 &S0 &T5 &U0 &Y1
S00=001 S01=000 S02=043 S03=013 S04=010 S05=008 S06=002
S07=060 S08=002 S09=006 S10=014 S11=070 S12=050 S13=000
S15=000 S16=000 S18=010 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
Step 2: Now that you can see your modem’s settings, it is time to alter the register to match this
information sheet, type the command prefix AT, followed by the register letter and desired value.
For example, if the modem had register F set to 0, register X set to 4 and register &N set to 0,
those registers need to change. (The example registers are highlighted in bold lettering.)
You can change each register individually: By typing ATF1, then press your enter key F0 will
change to F1. AT is the beginning of the modem command, F is the register value, and 1 is the
number you are changing it to.
ATX1, then press your enter key.
AT&N6, then press your enter key.
Or combine the necessary changes into one command:
ATF1X1&N6, then press your enter key.
Step 3: Then the changes must be saved to the modem's memory: To do this type AT&W0, then
press your enter key. Then type ATI4 again to confirm the changes were made.
When confirmed, power off the modem, set switches 1 and 4 down, the rest of them up.
Step 4: Verify the cable to be used between the ICP/EL and the modem. You will need two
cables with the USR 33.6 and V.92 modems.
Cable Number 1: (to program the modem from your laptop, a null modem cable must be used and your
dip switches must be set to 1, 3, and 8 down all others up.)
DB 9 DB25
1 open
2 --------- 3
3 --------- 2
4 open
5 --------- 7
6 open
7 open
8 open
9 open
Cable Number 2: (for the modem to PBX connection a straight thru cable must be used and switches 1
and 4 are down and everything else is up.)
DB9 DB25
1 open
2 --------- 2
3 --------- 3
4 open
5 --------- 7
6 open
7 open
8 open
9 open