Telstar – Troubleshooting

Here are aa few settings that may help get connected.

PSTN Access

US Robotics Modem (Courier V. Everything, Dual, HST Dual etc.)

When accessing via PSTN (Public Switched Telephone Network) the modem must be set to V23 1200/75 baud. That is receiving at 1200baud and transmitting at 75baud.

The most common issue witnessed by users connecting is with US Robotics modems where the S register S34 has not been set. The full configuration for US Robotics modems is:

AT&F
AT&B1
AT&H1
ATS0=1
ATS34=8
ATS19=2
ATE0
AT&W

Dowty Quattro (DM424X) Modem

AT&F
    AT&D2
    AT&C1
    AT&I3
    AT&R1 (should be default but seems not to be)
    ATS0=1
    ATS37=60
    AT&W

B   Bell/CCITT     0          &M  Sync Mode      0
E   Echo           0          &P  MB Ratio       1
F   Format         3          &R  RTS/CTS        1
L   Loudness       2          &S  Switch Ctrl    0
M   Speaker        1          &T  RDL Inhibit    4
Q   Quiet          0          &U  User Flow      0
V   Verbose        1          &V  Dumb           0
X   Results        4          &X  Tx Clk Source  0
Y   Long Space     0          &Y  Ctrl Port      0
&A  Auto-rate      0          *A  Auto-sync      0
&B  Busy           0          *D  DTR Dial       0
&C  DCD Option     1          *F  VF Flow Ctrl   0
&D  DTR Option     2          *G  Calling Tone   0
&E  Error Corr     0          *K  Multi Mode     0
&G  Guard Tone     2          *R  Remote Ctrl    1
&I  Const Speed    3          *U  Multi User     0
&K  Flow Ctrl      3          *X  Sync Clocks    0
&L  Leased Line    0          *Y  Break          0

OK


Reg  Dec  Hex        Reg  Dec  Hex        Reg  Dec  Hex
-------------        -------------        -------------
  0    1   01         17    0   00         34   50   32
  1    0   00         18    0   00         35    0   00
  2   43   2B         19    0   00         36    5   05
  3   13   0D         20    0   00         37   60   3C
  4   10   0A         21   52   34         38  242   F2
  5    8   08         22  246   F6         39   17   11
  6    4   04         23  133   85         40   19   13
  7   40   28         24    0   00         41  249   F9
  8    4   04         25   15   0F         42  251   FB
  9    6   06         26    0   00         43    0   00
 10   14   0E         27    0   00         44    0   00
 11    0   00         28    0   00         45    6   06
 12   50   32         29    0   00         46    0   00
 13    0   00         30    0   00         47   13   0D
 14  168   A8         31  131   83         48   13   0D
 15    0   00         32  104   68         49   17   11
 16    0   00         33    0   00         50   19   13

OK

Grandstream 802 Settings

These are the settings that have been found to be the best when calling Telstar from a SIP line with a Grandstream ATA 802 device (or similar).