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The following table shows all device parameters which can be defined for modem communication in the device object's connection description.
Par. |
Values |
Settings |
Description |
/IF |
modem1 ... modemX |
None |
Modem device Example: "/IF=modem1" |
/MO |
Modem name |
None |
Name of the modem, as it appears in the Setup dialog box (Control Panel -> Modems). The string must be enclosed in single quotation marks. If single quotes are to be used in the string, then the whole expression needs to be enclosed by another set of single quotes (e.g. m'56k is specified as /MO='m''56k' ). Example: "/MO='MicroLink 56k'" |
/TN |
Telephone number |
None |
Telephone number. Telephone number to be dialed according to the "ITU-T Recommendation E.123" format, e.g. +43(7748)6586. The entire telephone number should always be specified (with country code). Conversions to the actual number are done automatically. This string must be written in single quotation marks. If a call is being waited for, an empty string should be entered (/TN=''). Example: "/TN='+43(7748)6586'" |
/MR |
0 - INFINITE |
INFINITE |
Maximum number of unsuccessful dialing attempts. Specifies how often it should be attempted to re-establish a broken connection. If "INFINITE" is specified, redialing continues indefinitely. A value 0 means that no attempts at redialing are made. The parameter /MR is only relevant when /TN is not empty. Example: "/MR=50", "/MR=INFINITE" |
/RI |
0 - 3600 |
60 |
Time interval between dialing attempts in seconds. If a dialing attempt fails, then this time interval is always observed before another attempt is made. The Parameter /RI is only relevant when /TN is not empty. Example: "/RI=120" |
/IT |
0 - 60000 |
40 |
Interval timeout (msec) Defined as the maximum time that can pass between receiving two consecutive characters. The NET2000 protocol uses this time to recognize the end of a received frame. Example: "/IT=100" |
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For additional parameters, see NET2000 protocol parameters. |
The /MO and /TN parameters must always be specified along with the /IF parameter.
The operating system automatically reads the serial interface. This function is carried out using a buffer where the data received is stored. The operating system stops reading if one of the following situations occurs:
1.The buffer is full.
2.A time span longer than the interval timeout has passed since the last character was received.
Because of this, setting the /IT parameter for the interval timeout is extremely important. If the interval timeout is too small, NET2000 frames can be lost. This would cause the connection to be broken. If it is too big, data throughput is reduced because the interval timeout passes before the PC detects a received frame. The preset value of 40 ms has been selected due to measurements that show that a modem (using internal buffering) can insert breaks of approx. 35 ms into byte flow. Normally, it is not necessary to choose another value. However, increasing the timeout value may be necessary e.g. when using other types of modems or when line quality is poor (modems have their own transfer security with automatic send retry).
Connection description example:
CD="/IF=modem1 /MO='ZyXEL MODEM Omni 288S' /TN='+43(7748)999'"