Configuring a US Robotics COURIER modem for use on a UNIX host

This modem can be used "out of the box", with good results.

Start by ensuring the DIP switches are in a good starting configuration. From switch one: OFF, OFF, ON, OFF, ON, OFF, OFF, ON, ON(*), OFF.

(*) Moving DIP switch #9 from OFF to ON enables command mode after typing +++. Leaving switch #9 in the OFF position (the factory default) simply causes the call to be dropped when you type +++.

After connecting to the computer, enter "ATD", and adjust the volume control (slide lever under front right corner of modem) until dial tone can be clearly heard.

at&f1	Recall factory configuration #1
att	touch-tone dialing
atm0	speaker turned off  (M1 --> speaker on when awaiting remote answer)
ats32=6	voice/data button resets modem

These notable settings are included in the f1 defaults.

atx7	extended result codes (f1 default)
at&a3	Full protocol codes (f1 default)
at&h1	Transmit: Hardware flow control (f1 default)
at&i0	Receive: Software flow control disabled (f1 default)
at&k1	compression enabled (f1 default)

A convenient cut-n-paste version:

at&f1 t m0 s32=6 &w

USRobotics Courier V.Everything Settings...

   B0  C1  E1  F1  M0  Q0  V1  X1

   &A1  &B0  &C1  &D2  &G0  &H0  &I0  &K1  &L0  &M4  &N0
   &P0  &R1  &S0  &T5  &X0  &Y1  %N6  

   S00=000  S01=000  S02=043  S03=013  S04=010  S05=008  S06=002  S07=060  
   S08=002  S09=006  S10=007  S11=070  S12=050  S13=000  S14=000  S15=000  
   S16=000  S17=000  S18=000  S19=000  S20=000  S21=010  S22=017  S23=019  
   S24=150  S25=005  S26=001  S27=000  S28=008  S29=020  S30=000  S31=000  
   S32=006  S33=000  S34=000  S35=000  S36=000  S37=000  S38=000  S39=000  
   S40=000  S41=000  S42=126  S43=200  S44=015  S45=000  S46=000  S47=000  
   S48=000  S49=000  S50=000  S51=000  S52=000  S53=000  S54=064  S55=000  
   S56=000  S57=000  

   LAST DIALED #:                                       


An alternative

On the Sun workstations running SunOS 4, the "tip dialer" command doesn't respect the hardware flow control flag in /etc/remote, and so any use of the modem to receive at high speed is likely to provoke the Sun into sending an ^S/^Q sequence. This will go to the far end of the connection and be echoed, rather than having the desired effect of slowing down the data transfer. Loss of characters is possible. The most convenient workaround for this is to have the modem power-up using ^S/^Q "software" flow control, and to have any PPP or dialer scripts switch the modem into "hardware" flow control.

A convenient cut-n-paste version:

at&f1 &h2 &i2 t m0 s32=6 &w

Then, in the chat / PPP connect mode, dial the call as:

AT &H1 &I0 DT 5551212
Note that you may have to remove the spaces to prevent confusing your scripting language.

What is ARQ?

The manual states that ARQ means Automatic Repeat reQuest, a shorthand for saying that the modem connection has at least one of the possible error correction protocols enabled and operating.

The ARQ indicator on the front pannel is on while an error corrected call is in progress; the manual says that the indicator turns off briefly whenever data is being retransmitted to correct for an error.

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