 (At the DTE)
 (At the DTE)
 (At the DCE)
 (At the DCE)
37 PIN D-SUB MALE at the DTE (Computer).
37 PIN D-SUB FEMALE at the DCE (Modem).
| Pin | Name | Dir | Description | 
|---|---|---|---|
| 1 | GND |  | Shield Ground | 
| 2 | SRI |  | Signal Rate Indicator | 
| 3 | n/c | - | Spare | 
| 4 | SD |  | Send Data | 
| 5 | ST |  | Send Timing | 
| 6 | RD |  | Receive Data | 
| 7 | RTS |  | Request To Send | 
| 8 | RR |  | Receiver Ready | 
| 9 | CTS |  | Clear To Send | 
| 10 | LL |  | Local Loopback | 
| 11 | DM |  | Data Modem | 
| 12 | TR |  | Terminal Ready | 
| 13 | RR |  | Receiver Ready | 
| 14 | RL |  | Remote Loopback | 
| 15 | IC |  | Incoming Call | 
| 16 | SF/SR |  | Select Frequency/Select Rate | 
| 17 | TT |  | Terminal Timing | 
| 18 | TM |  | Test Mode | 
| 19 | GND |  | Ground | 
| 20 | RC |  | Receive Twister-Pair Common | 
| 21 | GND |  | Spare Twister-Pair Return | 
| 22 | /SD |  | Send Data TPR | 
| 23 | GND |  | Send Timing TPR | 
| 24 | GND |  | Receive Timing TPR | 
| 25 | /RS |  | Request To Send TPR | 
| 26 | /RT |  | Receive Timing TPR | 
| 27 | /CS |  | Clear To Send TPR | 
| 28 | IS |  | Terminal In Service | 
| 29 | /DM |  | Data Mode TPR | 
| 30 | /TR |  | Terminal Ready TPR | 
| 31 | /RR |  | Receiver TPR | 
| 32 | SS |  | Select Standby | 
| 33 | SQ |  | Signal Quality | 
| 34 | NS |  | New Signal | 
| 35 | /TT |  | Terminal Timing TPR | 
| 36 | SB |  | Standby Indicator | 
| 37 | SC |  | Send Twister Pair Common |