Pin No. | Name | Dir | Notes/Description |
1 | PGND | IN | Protective ground. Cable shield connected here. |
2 | TD | OUT | Transmit Data (a.k.a TxD, Tx). Sending data to DCE from DTE. |
3 | RD | IN | Receive Data (a.k.a RxD, Rx). Arriving data from DCE. |
4 | RTS | OUT | Request to Send. Raised by DTE when it wishes to send. Expects CTS from DCE. |
5 | CTS | IN | Clear to Send. Raised by DCE in response to RTS from DTE |
6 | DSR | IN | Data Set Ready. Raised by DCE to indicate ready. |
7 | SGND | - | Signal ground / common for all other signals. |
8 | DCD | IN | Data Carrier Detect. Raised by DCE when modem synchronized. |
9 | + | OUT | +VOLTAGE. Defined but typically not implemented. |
10 | - | OUT | -VOLTAGE. Defined but typically not implemented. |
11 | - | - | Unassigned pin. No connection. |
12 | sDCD | IN | Secondary Data Carrier Detect (or Received Line Signal Detector) |
13 | sCTS | IN | Secondary Clear To Send. |
14 | sTD | OUT | Secondary Transmit Data (sTxD). |
15 | TSET | IN | Transmitter Signal Element Timing. |
16 | sRD | IN | Secondary Received Data (sRxD). |
17 | RSET | IN | Receiver Signal Element Timing. |
18 | LL | OUT | Local Loopback. |
19 | sRTS | OUT | Secondary Request To Send. |
20 | DTR | OUT | Data Terminal Ready. Typically raised when the data terminal (PC or PLC) is powered and ready. |
21 | RL | OUT | Remote Loopback. |
22 | RI | IN | Ring Indicate. Raised by DCE and sent to DTE to tell DTE to get ready... a call is coming. |
23 | sCTS | - | Data Signal Rate Selector. Can sent by either DCE or DTE. |
24 | ETSET | OUT | External Transmit Signal Element Timing. |
25 | TM | IN | Test Mode. |
Pin No. | Name | Dir | Notes/Description |
1 | DCD | IN | Data Carrier Detect. Raised by DCE when modem synchronized. |
2 | RD | IN | Receive Data (a.k.a RxD, Rx). Arriving data from DCE. |
3 | TD | OUT | Transmit Data (a.k.a TxD, Tx). Sending data from DTE. |
4 | DTR | OUT | Data Terminal Ready. Raised by DTE when powered on. In auto-answer mode raised only when RI arrives from DCE. |
5 | SGND | - | Ground |
6 | DSR | IN | Data Set Ready. Raised by DCE to indicate ready. |
7 | RTS | OUT | Request To Send. Raised by DTE when it wishes to send. Expects CTS from DCE. |
8 | CTS | IN | Clear To Send. Raised by DCE in response to RTS from DTE. |
9 | RI | IN | Ring Indicator. Set when incoming ring detected - used for auto-answer application. DTE raised DTR to answer. |