DEVICE
| SIGNAL
| MEANING
|
Computer
| DTR+
| I want to call another system. Are you ready?
|
Modem
| DSR+
| Yes, I’m ready. Go ahead and dial.
|
Modem
| DCD+
| I’ve got your party, sir.
|
Computer
| RTS+
| Can I send data now?
|
Modem
| CTS+
| Sure. Go ahead.
|
Computer
| TxD...
| Data sent out.
|
Modem
| ...RxD
| Data Received. Previous four steps may be repeated, with either device in the
sending role.
|
Computer
| DTR-
| I’m done. Please hang up.
|
Modem
| DCD-
| Whatever you say.
|
All of the above sounds good in theory, but in practice it will not always
work. Connecting a computer to a modem is generally easy, since a DTE to DCE
connection is what RS-232 was made for. A straight-through cable connecting pins 1
through 8 and 20 (or all 25 pins) will usually do the trick.