This section contains information about:
Your computer sends a Data Terminal Ready (DTR) signal to the Courier 56K Business Modem when it is ready to send and receive data. The &Dn command tells the modem how to respond to the DTR signal.
| For your modem to | Command |
| Ignore the state of DTR and act as if DTR is always present. Use this command with equipment that cannot provide DTR. | AT&D0 |
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Enter online Command Mode during a call by dropping DTR, if issued before connecting with another device. Most communications software packages have a method for toggling DTR. Refer to your software’s manual for details. |
AT&D1 |
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Respond normally to the DTR signal. The Courier 56K Business Modem will not accept commands until your computer sends a DTR signal. The call will end when the DTR signal is dropped. To change the DTR recognition time, set S-Register 25. Refer to the S-Registers appendix in this guide for more information. |
AT&D2 |
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Respond normally to the DTR signal and reset on DTR drop. The Courier 56K Business Modem will not accept commands until your computer asserts a DTR signal. The call will end when the DTR signal is dropped. To change the DTR recognition time, set S-Register 25. Refer to the S-Registers appendix in this guide for more information. |
AT&D3 |
Example: Sending AT&D1 before connecting with another device, dropping DTR will enter Command Mode.
Note: DIP switch 1 overrides the &Dn setting at power on or reset.
Under normal conditions, the Courier 56K Business Modem sends a Data
Set Ready (DSR) signal to your computer when it is ready to send and receive
data.
CAUTION: Do not change the default setting of &S0 unless you know that your installation requires a different setting. Few communications programs, if any, will require the Courier 56K Business Modem to control DSR (&S1).
Use the following command to control how the modem sends the DSR signal.
| For your modem | Command |
| To assert the DSR signal at all times. | AT&S0 (Default) |
| When originating a call, to assert the DSR signal after dialing when the Courier 56K Business Modem detects the remote analogue device’s answer tone. | AT&S1 |
| When answering a call, to assert DSR after the Courier 56K Business Modem sends its answer tone. | AT&S1 |
| To assert a pulsed DSR signal, followed by a Clear to Send (CTS) signal, after sending Carrier Detect (CD). Use this option for specialised equipment such as automatic callback units. | AT&S2 |
| To assert a pulsed DSR signal after sending Carrier Detect (CD). | AT&S3 |
| To assert a DSR signal to your computer at the same time the Courier 56K Business Modem asserts the CD signal. | AT&S4 |
| To send DSR normally (with CTS) after sending CD. In order to change the DSR pulse time (in 30-millisecond increments), set S-Register 24. Refer to the S-Registers appendix in this guide for more information. |
AT&S5 |
Example: Issuing AT&S3 configures the Courier 56K Business Modem to send a pulsed DSR signal after sending the Carrier Detect (CD) signal.
Carrier means there is communication with the device on the other end of the connection. Under normal conditions, the Courier 56K Business Modem sends a Carrier Detect (CD) signal in response to esablishing a connection with another modem. You can use the AT&Cn command to control how the Courier 56K Business Modem sends the CD signal.
| For your modem to | Command |
| Have CD always ON. | AT&C0 |
| Send CD normally (the Courier 56K Business Modem sends a CD signal when it connects with another device, and drops the CD signal when it disconnects). (Default) | AT&C1 |
Note: DIP switch 6 overrides the &Cn setting at power on or reset.