MULTI-TECH SYSTEMS, INC.
MT224AH
Modem Type | Data (synchronous/asynchronous) |
Maximum Data Rate | 2400bps |
Data Bus | External |
Data Modulation Protocol | Bell 103A/212A ITU-T V.21, V.22, V.22bis, V.23 |
Error Correction/Compression | MNP5, V.42, V.42bis |

CONNECTIONS | |||
Purpose | Location | Purpose | Location |
DC power | CN1 | Line in | CN4 |
RS-232/422 | CN2 | Power switch | SW1 |
Line out | CN3 | Volume | R1 |
ASYNCHRONOUS/SYNCHRONOUS | |
Settings | SW5/D |
Synchronous | On |
| » Asynchronous | Off |
AUTO-ANSWER | |
Settings | SW4/E |
| » Enable auto answer/originate | On |
Disable/answer | Off |
Note: When SW5/B is set for Lease Line operation, the options on this switch change to Originate and Answer | |
BLIND/WAIT DIALING | |
Settings | SW5/C |
Wait for dial tone | On |
| » Blind dialing | Off |
BAUD RATE | |
Settings | SW2 |
1200bps | Position 1 |
300bps | Position 2 |
2400bps | Position 3 |
CD/DSR | |
Settings | SW4/F |
| » CD/DSR normal | On |
CD/DSR forced high | Off |
COMMAND CHARACTERS | |
Settings | SW4/D |
| » Echo enable | On |
Echo disable | Off |
COMMAND MODE | |
Settings | SW4/H |
Disable | On |
| » Enable | Off |
CTS | |
Settings | SW5/A |
| » CTS forced high | On |
CTS normal | Off |
CTS/RTS | |
Settings | JP2 |
| » CTS follows RTS | Pins 1 & 2 closed |
CTS forced high until disconnect | Pins 2 & 3 closed |
DSR | |
Settings | JP3 |
| » DSR follows CD | Pins 2 & 3 closed |
| DSR follows OH | Pins 1 & 2 closed |
FORCED DTR | |
Settings | SW4/A |
DTR normal | On |
| » DTR forced high | Off |
JACK TYPE | |
Settings | SW4/G |
| » RJ11 | On |
RJ12/13 | Off |
RESULT CODES | |
Settings | SW4/B |
| » Verbose | On |
Terse | Off |
RESULT CODES | |
Settings | SW4/C |
Disable | On |
| » Enable | Off |
RTS | |
Settings | JP1 |
| » RTS forced high | Pins 1 & 2 closed |
RTS normal | Pins 2 & 3 closed |
SWITCHED/LEASE LINE | |
Settings | SW5/B |
| » Switched | On |
Lease line | Off |
VOICE/DATA MODE | |
Settings | SW3 |
Answer | Position 1 |
Originate | Position 2 |
DIAGNOSTIC LED(S) | |||
LED | Color | Status | Condition |
SD | Red | On | Modem is transmitting data |
SD | Red | Off | Modem is not transmitting data |
RD | Red | On | Modem is receiving data |
RD | Red | Off | Modem is not receiving data |
CD | Red | On | Carrier signal detected |
CD | Red | Off | Carrier signal not detected |
24 | Red | Blinking fast | Modem connected at 2400bps in reliable mode |
24 | Red | Blinking slow | Modem connected at 2400bps with data compression |
24 | Red | Off | Modem not connected at 2400bps |
12 | Red | Blinking fast | Modem connected at 1200bps in reliable mode |
12 | Red | Blinking slow | Modem connected at 1200bps with data compression |
12 | Red | Off | Modem not connected at 1200bps |
OH | Red | On | Modem is off-hook |
OH | Red | Off | Modem is on-hook |
TR | Red | On | DTR signal is high |
TR | Red | Off | DTR signal is low |
Proprietary AT Command Set
BLIND DIALING | |
Type: | Configuration |
Format: | AT [cmds] Bn [cmds] |
Example: | AT B0 <CR> |
Description: | Selects blind dial or wait-for-dial-tone. |
Command | Function |
| » B0 | Modem will blind dial. |
| B1 | Modem will wait for dial tone before dialing. |
CD SIGNAL | |
Type: | Configuration |
Format: | AT [cmds] &Cn [cmds] |
Example: | AT &C3 $D0 <CR> |
Description: | Configures the behavior of the carrier detect signal. |
| Command | Function |
| &C0 | CD forced high. |
| » &C1 | CD normal. |
| &C2 | CD forced high except during disconnect. |
COMMAND SET | |
Type: | Configuration |
Format: | AT [cmds] &Qn [cmds] |
Example: | AT &Q0 <CR> |
Description: | Selects standard Hayes or custom command sets. |
| Command | Function |
| » &Q0 | Multi-Tech custom command set enabled. |
| &Q1 | Standard Hayes command set enabled. |
DIAL STORED PHONE NUMBER | |
Type: | Immediate |
Format: | AT [cmds] Nn1 [Nn2, Nn3...] |
Example: | ATM0 N1N3N5 <CR> |
Description: | Dials stored phone number(s). If the first number is busy, the modem will proceed to the next number in the list. |
DSR/CTS/CD TIMEOUT | |
Type: | Register |
Format: | AT [cmds] S24=n [cmds] |
Example: | ATS24=40 <CR> |
Default: | 20 |
Range: | 0-255 |
Unit: | 50 ms |
Description: | Sets the time to drop the DSR, CTS, and CD signals to hangup. |
DTR DIALING | |
Type: | Configuration |
Format: | AT [cmds] $Dn [cmds] |
Example: | AT $D1 DT555-1212 <CR> |
Description: | Selects the DTR dialing function. |
| Command | Function |
| » $D0 | DTR dialing disabled. |
| $D1 | DTR dialing enabled. |
DTR TIMEOUT | |
Type: | Register |
Format: | AT [cmds] S25=n [cmds] |
Example: | ATS25=30 <CR> |
Default: | 0 |
Range: | 0-255 |
Unit: | .1 second |
Description: | Sets the time to drop the DTR signal to hangup. |
Note: | Setting S25 to 0 sets the DTR timeout to 50 ms. |
DUPLEX | |
Type: | Configuration |
Format: | AT [cmds] Fn [cmds] |
Example: | AT F1 &W <CR> |
Description: | Controls duplex mode. |
| Command | Function |
| F0 | Half duplex enabled. |
| » F1 | Full duplex enabled. |
HELP SCREENS | |
Type: | Immediate |
Format: | AT $Hn |
Example: | AT $H1 <CR> |
Description: | Shows modem help screens. |
Command | Function |
$H1 | Shows help screen 1. |
$H2 | Shows help screen 2. |
$H3 | Shows help screen 3. |
$H4 | Shows help screen 4. |
LIST CONFIGURATION | |
Type: | Immediate |
Format: | AT Ln |
Example: | AT L5 <CR> |
Description: | Lists modem configuration. |
Command | Function |
L0 | Lists all phone numbers in memory. |
L5 | Lists all settings. |
L6 | Lists the values of all S-registers. |
LOOPBACK TEST MODE | |
Type: | Configuration |
Format: | AT [cmds] Un [cmds] |
Example: | AT U2 &W <CR> |
Description: | Places modem in test mode. |
| Command | Function |
U0 | Begin local analog loopback test in originate mode. |
U1 | Begin local analog loopback test in answer mode. |
U2 | Request remote digital loopback |
U3 | Begin local digital loopback. |
PROTOCOL | |
Type: | Configuration |
Format: | AT [cmds] &Vn [cmds] |
Example: | AT &V1 <CR> |
Description: | Selects the protocol for low-speed data calls. |
Command | Function |
| &V0 | Bell protocols. |
| » &V1 | ITU-T protocols. |
REDIAL | |
Type: | Immediate |
Format: | A: |
Example: | A: |
Description: | Redials the last number dialed until it is no longer busy. |
Note: | Do not precede this command with AT or follow it with <CR>. |
STORE PHONE NUMBER IN NVRAM | |
Type: | Configuration |
Format: | AT [cmds] D<#>N<0-9> |
Example: | ATD1(303)-443-3323N6 <CR> |
Description: | Stores a phone number in the modem’s memory. Only the dialstring before the N will be stored. |
WAIT FOR DIAL TONE | |
Type: | Immediate |
Format: | AT [cmds] W [cmds] |
Example: | AT W <CR> |
Description: | Wait for new dial tone. |