Using V.32/V.34 Modems with DCB muxes
Note: Sync operation is by far the easiest and most reliable method to use for dial-up multiplexor systems. Many new 28.8 and 33.6 modems
no longer support sync operation. Boca, Hayes, Zoom are among the manufacturers known to have dropped this feature from their newest
modem models. Check specs carefully before you decide which modem to buy.
Dial-up (Using terminal ATD ... dialing)
Sync - preferred
Switch settings for mux
Host Mux Network - 2 UP (sync leased line)
Remote Mux Network - ALL DOWN (sync dial-up)
Soft settings for modem
Host Modem - AT&F&Q1&C1&K0E0Q1S0=1&W
Remote Modem - AT&F&Q1&C1&K0&W
Async
Note: When configuring your modem for async operation, use a terminal or PC set at the same baud rate as you intend to
use for the mux network.
Switch settings for mux
Host Mux Network - 1, 2 UP and 4, 5, 6 for desired speed
Remote Mux Network - 1 UP and 4, 5, 6 for desired speed
| 4 | 5 | 6 | Rate |
| UP | UP | DN | 38,400 |
| UP | UP | UP | 19,200 |
| DN | DN | DN | 9,600 |
| DN | DN | UP | 4,800 |
| DN | UP | DN | 2,400 |
| UP | DN | DN | 1,200 |
Soft settings for modem
Host Modem - AT&F&Q6&K0&C1E0Q1S0=1&W
Remote Modem - AT&F&Q6&D2&K0&C1&W
Auto Dial (on DTR transistion)
Sync
Switch settings for mux
Host Mux Network - 2 UP (sync leased line)
Remote Mux Network - ALL DOWN (sync dial-up)
Soft settings for modem
Host Modem - AT&F&Q1&C1&K0E0Q1S0=1&W
Remote Modem - AT&F&Z0=nnn-nnnn (Where nnn-nnnn is the number to dial)
AT&Q2&C1&K0&W
Note: Press the multiplexor RESET switch to force the modem to dial.
Modem AT commands and their meanings
Note: There are many variations in the supposed "Hayes Compatable" command set. This is especially true of newer V.34 models. If the
setup strings above do not appear to work, or return error messages, use the list below to find the correct commands for your particular
modem to perform the indicated functions.
&F - restore factory defaults
&W - write settings to memory and save
&Q1 - force sync mode
&Q2 - force sync mode with auto dial
&C1 - DCD follows call progress (DCD not forced on)
&K0 - disable flow control
E0 - turn off command echo
Q1 - disable result codes
S0=1 - force auto answer mode
&Q6 - set buffered async mode (disables autobaud, allows DTE and line speed to differ)
&D2 - allows DTR to follow interface in Q6 mode (DTR not forced on)
&Z0 - store number for auto dial