Sample Data Modem Event Log

Following is a sample data modem event log, with annotations added to the logged events.

05:02:55 05-25-1994 - TI V.32bis-V.17 Internal in use.
05:02:55 05-25-1994 - Modem type: TI V.32bis-V.17 Internal
 

An application has called TAPI to open this modem's line handle. UNIMODEM.TSP called the Win32 function CreateFile("TI V.32bis-V.17 Internal"...) to open a file handle to UNIMODEM.VXD for this modem.

05:02:56 05-25-1994 - 38400,N,8,1
 

Unimodem has called VCOMM to open the correct serial port for this modem, and set its default COM port settings.

05:02:56 05-25-1994 - Initializing modem.
05:02:56 05-25-1994 - Send: AT
 

Unimodem sends an "AT" to initialize the modem's autobaud setting.

05:02:57 05-25-1994 - Recv: ATfOK
05:02:57 05-25-1994 - Interpreted response: Ok
 

The "ATcr" is echoed back by the modem, along with an "OK" response code. Unimodem discards the echoed command, and correctly interprets the OK response.

05:02:57 05-25-1994 - Send: AT &F0 
05:02:59 05-25-1994 - Recv: AT &F0 fOK
05:02:59 05-25-1994 - Interpreted response: Ok
 

Unimodem sends the first Init string specified in the INF, discards the echoed command, and interprets the OK response correctly.

05:02:59 05-25-1994 - Send: AT E0 Q0 V0 W1 T L2 M1 &C1 
05:03:01 05-25-1994 - Recv: AT E0 Q0 V0 W1 T L2 M1 &C1 0
05:03:01 05-25-1994 - Interpreted response: Ok
 

Unimodem sends the second Init string from the INF. The command is echoed back, but notice that numeric response codes are now in use.

05:03:01 05-25-1994 - Send: AT &D2 &S0 X4 %C1 \J0 \N7 \Q3 \V1 \T0 
05:03:03 05-25-1994 - Recv: 0
05:03:03 05-25-1994 - Interpreted response: Ok
 

Unimodem successfully sends the third Init string from the INF. Note that this command was not echoed back by the modem.

05:03:03 05-25-1994 - Send: ATS7=50\T0L2M1%C1\N7\Q3B1X4
05:03:04 05-25-1994 - Recv: 0
05:03:04 05-25-1994 - Interpreted response: Ok
 

This is the dynamic initialization stage. Unimodem sent a string to configure the modem to settings requested by the user and/or application. The command string is built dynamically based on registry keys, originally specified by "Settings" values in the INF file.

05:03:04 05-25-1994 - Dialing ''.
05:03:04 05-25-1994 - Send: ATX4
05:03:06 05-25-1994 - Recv: 0
05:03:07 05-25-1994 - Interpreted response: Ok
 

Unimodem first sets dial tone detection on.

05:03:07 05-25-1994 - Send: ATDT;
05:03:09 05-25-1994 - Recv: 0
05:03:09 05-25-1994 - Interpreted response: Ok
 

Unimodem takes the modem off-hook.

05:03:09 05-25-1994 - Dialing '9242 9992'.
05:03:09 05-25-1994 - Send: ATX4
05:03:11 05-25-1994 - Recv: 0
05:03:11 05-25-1994 - Interpreted response: Ok
 

Unimodem sets dial tone detection on again (probably a bug).

05:03:11 05-25-1994 - Send: ATDT9242 9992;
05:03:15 05-25-1994 - Recv: 0
05:03:15 05-25-1994 - Interpreted response: Ok
 

Unimodem dials the phone number provided by the application via a TAPI lineMakeCall function.

05:03:15 05-25-1994 - Originating the call.
05:03:15 05-25-1994 - Send: ATX3D
 

Unimodem originals the call. Note that 'X3' is included because this modem will not work correctly without it. Some modems do not require this.

05:03:30 05-25-1994 - Recv: 527769
05:03:30 05-25-1994 - Interpreted response: Ignore
 

"Ignore" is misleading. Here, Unimodem recognized "52" as a call progress response code.

05:03:30 05-25-1994 - Recv: 7769
05:03:30 05-25-1994 - Interpreted response: Ignore
 

Unimodem recognized "77" as a call progress response code.

05:03:30 05-25-1994 - Recv: 69
05:03:30 05-25-1994 - Interpreted response: Connect
 

Unimodem recognized "69" as indication of a connection.

05:03:30 05-25-1994 - Connection established at 14400bps.
05:03:30 05-25-1994 - Error-control activated.
05:03:30 05-25-1994 - No data compression, or modem does not support compression reporting.
 

Unimodem knows that this is a 14400 call with error compression but no data compression, based on the "527769" response codes.

The call is now in progress, in use by the application.

05:03:41 05-25-1994 - Remote modem hung up.
 

Unimodem detected carrier loss. The call was disconnected by the other computer. This output would appear different if Unimodem had been called to disconnect.

05:03:41 05-25-1994 - Hanging up the modem.
 

Unimodem dropped DTR to cause the modem to hang up.

05:03:41 05-25-1994 - TI V.32bis-V.17 Internal closed.
 

UNIMODEM.TSP closed its Win32 file handle to the modem.