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Basic CT Networking
Loop Network
Modem Networking
Multi COM Port Boards |
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There are two types of RS-232 devices and four types of connectors:
- DTE - Data Terminal Equipment
- Most computers and terminals
- DCE - Data Communications Equipment
- Most modems and TNCs
The connectors are DB9 and DB25, both male and female. Most DTEs have male connectors
(at least IBM PC's), and most DCEs have female connectors.
DTE devices can be connected directly to DCE. If two DTE devices (two computers) are to
be connected, a NULL modem (cross-over cable) is needed.
The following table lists the pinning for various NULL modem cables. To build a cable,
pick two adjacent columns from the table. For example, to build a 25-pin
to 9-pin cable, work from columns 2 (DB-25 pin) and 3 (DB-9 pin).
| DB-25 pin |
DB-25 pin |
DB-9 pin |
DB-9 pin |
| 2 |
TxD |
3 |
RxD |
3 |
TxD |
2 |
RxD |
| 3 |
RxD |
2 |
TxD |
2 |
RxD |
3 |
TxD |
| 4 |
RTS |
5 |
CTS |
7 |
RTS |
8 |
CTS |
| 5 |
CTS |
4 |
RTS |
8 |
CTS |
7 |
RTS |
| 6 |
DSR |
20 |
DTR |
6 |
DSR |
4 |
DTR |
| 7 |
GND |
7 |
GND |
5 |
GND |
5 |
GND |
| 20 |
DTR |
6 |
DSR |
4 |
DTR |
6 |
DSR |
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