A serial device is the physical channel or port through which information is transmitted when you connect to a network. With Corel LINUX, a physical serial device, or port, is managed using an associated file located in the /dev directory. You must tell the operating system which file is associated with the serial device.
In the Corel LINUX operating system, the serial devices for outgoing connections are /dev/ttyS0 and /dev/ttyS1. These devices correspond to COM1 and COM2 in a DOS or Microsoft Windows operating system. For example, if your modem is attached using COM1, you specify /dev/ttyS0 as the serial device. The most common serial device used for making dial-up connection is your modem. If your modem is attached using COM2, you specify /dev/ttyS1 as the serial device.
Once you have specified the serial device to use for a dial-up connection, you can specify how information is passed through the connection, configure flow control, line termination, and connection speed. You can also set a lock file to prevent incoming calls from interrupting the dial-up connection, and set the amount of time Dial-Up waits for the "connect" response after dialing to another modem, before timing out and hanging up.
With Dial-Up, you can set the volume of the modem's dial sounds and the number of seconds it waits for a connection before stopping the dial-up attempt. You can also configure basic modem commands, such as the initialization string, connect response, hang-up response, and escape string. Modem commands in Dial-Up are preset to standard commands. Some modems require customized commands. Consult the modem manufacturer's documentation before editing modem commands. You can query the modem to ensure that the operating system recognizes the modem, and view its hardware properties. You can also access a mini-terminal that you can use to manually control the modem by typing modem commands in the terminal window.
Flow control
Flow control is the way in which your modem or serial device controls the speed at which data flows through the physical port. If your data flow rate (the speed at which the serial port sends information to the modem) is faster than your modem speed (the speed at which your modem sends data to the phone line), excess data accumulates in the modem buffer. To avoid an overflow of excess data in the modem, the flow control mechanism temporarily stops the flow of data until the modem has decreased the amount of data that has accumulated in its buffer.
There are three options for flow control in Corel LINUX: hardware control (CRTSCTS), software control (XON/OFF), and no flow control.
Using hardware flow is recommended because it responds faster and more reliably to excess data flow problems.
Line termination
Line termination sets the sequence of characters that tell the modem that a line of input data is complete. You can choose from three line termination settings:
CR (Carriage Return)
LF (Line Feed)
CR/LF (Carriage Return/ Line Feed)
Most modems use the CR setting. For more information about line termination settings that are appropriate for your modem, see the modem manufacturer's documentation.
Connection speed
Connection speed (or data flow rate) is the amount of data that the serial device transmits to the modem. Connection speed is measured in bits per second (bps). To maximize data flow, you should set your connection speed higher than your modem speed. You should also enable flow control to prevent excess data accumulation in the buffer. For example, if you use a 56K modem, you should set your connection speed to 230400 bps (230.4K) or 460800 bps (460.8K). If you use a 28.8K or 33.6K modem, you should set the connection speed to 115200 bps (115.2K).
Lock File Option
You can set Dial-Up to create a lock file when it connects to a PPP server. A lock file prevents other connections to or from the modem while it is connected to a server. For example, if you dial up a server using a phone line that also receives telephone calls or faxes, a lock file prevents an incoming telephone call from interrupting your dial-up connection.
Modem Commands
You can use Dial-Up to send commands to the modem. The commands are short ASCII strings. Some commands are used to configure the modem. For example, the command AT&K3 enables hardware flow control (CRTSCTS) between your computer and modem. Other commands make the modem perform an action. For example, the command ATDT5551234 causes the modem to dial the phone number 555-1234.
Corel LINUX provides preset modem commands that Dial-Up sends to the modem during the dial-up process. You can use the preset commands, or you can edit them, depending on your modem. Check your modem documentation to see if any of the following preset modem commands need to be changed for your computer:
Pre-Init Delay Controls The Number
Initialization String
Post-Init Delay
Init Response
Dial String
Connect Response
Busy Response
No Carrier Response
No Dialtone Response
Hangup String
Hangup Response
Answer String
Ring Response
Escape String
Escape Response
Guard Time
Volume Off/Low/High
You can use modem commands to manually control the modem from the Mini-Terminal window. You can also use them to execute commands during the connection process.