| Data Rate |
Data rate is the speed at which data travels between the modem and the computer, measured in bits-per-second. In order to successfully transfer data, both devices must transmit and receive at the same rate. When you use a modem with the 7318, you may use as many as three different data rates:
- The data rate between the 7318 and the modem.
It is recommended that you set the 7318 modem rate to a fixed rate. This eliminates a potential source of errors. When using a fixed rate, flow control must be operating properly in both directions (send and receive).
- The data rate at which the modem sends data over the phone wire.
The data rate used by the modem to send data over the telephone line is controlled by the type of modem. For example, a 2400 baud modem typically sends data at a maximum rate of 2400 baud. Current modems negotiate the speed at which they transmit data. This speed can be a function of the type of modems they are talking to and the line conditions. When viewed from the 7318 point of view, modems with v.42 or v.42bis capability implement compression on the data at a higher rate than their basic rating. Because of these variables, it is recommended that you set the modem to the fastest speed that the modem supports and use flow control to manage the rate compression.
- The data rate of the corresponding modem on the other side of the connection.
The other end of the connection faces the same issues for the data rate between the 7318 and the modem and the data rate over the telephone wire. If 9600 baud is used on one end, it is not required that 9600 be used on the other end.
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| Parity |
Parity is not as important to a modem as it is to other devices, such as terminals. Modems can use an error correction and detection scheme that is more sophisticated than parity on the phone line. Also, data errors are less likely on a short cable typically used between a modem and a 7318.
The parity setting on the host must match the parity setting of the device to which you are communicating. The modem transparently replicates the parity through the telephone system, so the setting on both sides must agree. |
| Flow Control |
For modems, flow control can occur in three places:
- Between the modem and the 7318.
You can use either hardware or software flow control between the 7318 and the modem. It is recommended that you use hardware flow control, because this leaves Ctrl-S and Ctrl-Q available to applications and for you to use to manage the data displayed on the terminal screen.
- Between modems.
Modems use a form of flow control between themselves. This is a function of the modems and the standards with which they comply. This should not require any configuration on your part.
- Between the modem and the terminal device.
You can use either hardware or software flow control between the 7318 and the modem. We recommend you use hardware flow control, because this leaves Ctrl-S and Ctrl-Q available to applications and for you to use to manage the data displayed on the terminal screen. If you are communicating with another computer using an internal modem, this is not an issue.
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