The illustration above, provides a view of the standard RS232 signals as applied to the DB25 connector. Notice that signals/pins 2, 3, 4, 5, and 7, are the most commonly used signals for PC (DTE) to PacketRadio TNCees (DCE).
1. DB25
2. DE9 but more often called; the DB9
The RS-232 interface is ideal for the
data-transmission up to about 20,000 bits per second, to about fifty (50)
feet, or around fifteen (15) meters. RS-232 employs unbalanced signaling
and is usually used with DB25 connectors to interconnect data terminal
equipment [DTE] (computers, controllers, etc), to data communications
equipment [DCE] (terminal node controllers/TNCees modems, etc).
| DB-25
pin # |
DB-9
pin # |
Name | Description |
|---|---|---|---|
| 1 | PG | Protective Ground | |
| 2 | 3 | TD | Transmitted Data |
| 3 | 2 | RD | Received Data |
| 4 | 7 | RTS | Request To Send |
| 5 | 8 | CTS | Clear To Send |
| 6 | 6 | DSR | Data Set Ready |
| 7 | 5 | SG | Signal Ground |
| 8 | 1 | DCD | Data Carrier Detect |
| 9 | -- | Reserved for testing | |
| 10 | -- | Reserved for testing | |
| 11 | -- | Unassigned | |
| 12 | SDCD | Secondary Data Carrier Detect | |
| 13 | SCTS | Secondary Clear To Send | |
| 14 | STD | Secondary Transmitted Data | |
| 15 | TC | Transmission (signal) Timing | |
| 16 | SRD | Secondary Received Data | |
| 17 | RC | Receiver (signal) Timing | |
| 18 | -- | Unassigned | |
| 19 | SRTS | Secondary Request To Send | |
| 20 | 4 | DTR | Data Terminal Ready |
| 21 | SQ | Signal Quality Detect | |
| 22 | 9 | RI | Ring Indicator |
| 23 | -- | Data Rate Selector | |
| 24 | -- | Transmit (signal) Timing | |
| 25 | -- | Unassigned |
 |
