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Modem Won't Work with Cisco 3845

Posted on 2012-04-11
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Last Modified: 2013-08-01
I am trying to use a USR 5686G modem with a Cisco 3845 router via the AUX port.  I have followed the directions in this document http://www.cisco.com/en/US/tech/tk801/tk36/technologies_tech_note09186a0080094bbc.shtml, but still the modem is not responding correctly.  The problem is that when called, the modem answers, but it will not respond with the normal "squealing" tones.  Instead, there is silence for a few seconds followed by a loud hum.  I have worked with Cisco TAC, the staff of which could not find a solution. Here is my router config:

line aux 0
 password 7 xxxxx
 login
 modem InOut
 transport input all
 speed 115200
 flowcontrol hardware

Any ideas?
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Question by:nchc
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Darr247 earned 500 total points
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> the modem answers, but it will not respond with the normal "squealing"
> tones.  Instead, there is silence for a few seconds followed by a loud hum
I would connect that modem to a windows machine's serial port and 'Talk directly to COM#' port with hyperterminal.
Issue the command
ATE1V1Q0&C1&D2M1S0=1
and confirm you see an OK.
With the terminal still connected to the COM port the modem is on, call the modem from another modem and watch what it 'says' (e.g. when it receives a call you should actually see "ring" appear in the terminal... if you set S0=2 instead of S0=1, you should see "ring" appear twice before the modem picks up).

If it doesn't try to negotiate a connection at all, you should replace the modem.

AT = attention
E1 = echo commands
V1 = verbose results
Q0 = result codes enabled
&C1 = DCD state matches Carrier Detect
&D2 = if DCD goes from high to low, modem closes connection
M1 = speaker on during negotiation, off while connected
S0=1 = answer after 1 ring

Those are all fairly standard command between different modems, though really,  all "hayes compatible" means is that when you run AT the modem should reply OK.

About all other commands can differ from manufacturer to manufacturer.
e.g. To see what the current and stored configuration are, most modems use AT&V
Sometimes AT&V1 shows the previous session's statistics, sometimes it shows the 1st stored configuration.
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