Common names: EIA-449, RS-449, ISO 4902
Primary channel
(at the DTE)
(at the DCE)
CORRECT?
37 PIN D-SUB MALE at the DTE (Computer).
37 PIN D-SUB FEMALE at the DCE (Modem).
| Pin | Name | V.24 | Dir | Description | Type |
|---|---|---|---|---|---|
| 1 | 101 | Shield | Ground | ||
| 2 | SI | 112 | Signal Rate Indicator | Control | |
| 3 | n/a | n/a | unused | ||
| 4 | SD- | 103 | Send Data (A) | Data | |
| 5 | ST- | 114 | Send Timing (A) | Timing | |
| 6 | RD- | 104 | Receive Data (A) | Data | |
| 7 | RS- | 105 | Request To Send (A) | Control | |
| 8 | RT- | 115 | Receive Timing (A) | Timing | |
| 9 | CS- | 106 | Clear To Send (A) | Control | |
| 10 | LL | 141 | Local Loopback | Control | |
| 11 | DM- | 107 | Data Mode (A) | Control | |
| 12 | TR- | 108.2 | Terminal Ready (A) | Control | |
| 13 | RR- | 109 | Receiver Ready (A) | Control | |
| 14 | RL | 140 | Remote Loopback | Control | |
| 15 | IC | 125 | Incoming Call | Control | |
| 16 | SF/SR+ | 126 | Signal Freq./Sig. Rate Select. | Control | |
| 17 | TT- | 113 | Terminal Timing (A) | Timing | |
| 18 | TM- | 142 | Test Mode (A) | Control | |
| 19 | SG | 102 | Signal Ground | Ground | |
| 20 | RC | 102b | Receive Common | Ground | |
| 21 | n/a | n/a | unused | ||
| 22 | SD+ | 103 | Send Data (B) | Data | |
| 23 | ST+ | 114 | Send Timing (B) | Timing | |
| 24 | RD+ | 104 | Receive Data (B) | Data | |
| 25 | RS+ | 105 | Request To Send (B) | Control | |
| 26 | RT+ | 115 | Receive Timing (B) | Timing | |
| 27 | CS+ | 106 | Clear To Send (B) | Control | |
| 28 | IS | n/a | Terminal In Service | Control | |
| 29 | DM+ | 107 | Data Mode (B) | Control | |
| 30 | TR+ | 108.2 | Terminal Ready (B) | Control | |
| 31 | RR+ | 109 | Receiver Ready (B) | Control | |
| 32 | SS | 116 | Select Standby | Control | |
| 33 | SQ | 110 | Signal Quality | Control | |
| 34 | NS | n/a | New Signal | Control | |
| 35 | TT+ | 113 | Terminal Timing (B) | Timing | |
| 36 | SB | 117 | Standby Indicator | Control | |
| 37 | SC | 102a | Send Common | Ground |
Note: Direction is DTE (Computer) relative DCE (Modem).
| Name | Description | Function |
|---|---|---|
| AA | Shield Ground | Also known as protective ground. This is the chassis ground connection between DTE and DCE. |
| AB | Signal Ground | The reference ground between a DTE and a DCE. Has the value 0 Vdc. |
| BA | Transmitted Data | Data send by the DTE. |
| BB | Received Data | Data received by the DTE. |
| CA | Request To Send | Originated by the DTE to initiate transmission by the DCE. |
| CB | Clear To Send | Send by the DCE as a reply on the RTS after a delay in ms, which gives the DCEs enough time to energize their circuits and synchronize on basic modulation patterns. |
| CC | DCE Ready | Known as DSR. Originated by the DCE indicating that it is basically operating (power on, and in functional mode). |
| CD | DTE Ready | Known as DTR. Originated by the DTE to instruct the DCE to setup a connection. Actually it means that the DTE is up and running and ready to communicate. |
| CE | Ring Indicator | A signal from the DCE to the DTE that there is an incomming call (telephone is ringing). Only used on switched circuit connections. |
| CF | Received Line Signal Detector | Known as DCD. A signal send from DCE to its DTE to indicate that it has received a basic carrier signal from a (remote) DCE. |
| CH/CI | Data Signal Rate Select (DTE/DCE Source> |
A control signal that can be used to change the transmission speed. |
| DA | Transmit Signal Element Timing (DTE Source) |
Timing signals used by the DTE for transmission, where the clock is originated by the DTE and the DCE is the slave. |
| DB | Transmitter Signal Element Timing (DCE Source) |
Timing signals used by the DTE for transmission. |
| DD | Receiver Signal Element Timing (DCE Source) |
Timing signals used by the DTE when receiving data. |
| IS | terminal In Service | Signal that indicates that the DTE is available for operation |
| NS | New Signal | A control signal from the DTE to the DCE. It instructs the DCE to rapidly get ready to receive a new analog signal. It helps master-station modems rapidly synchronize on a new modem at a tributary station in multipoint circuits |
| RC | Receive Common | A signal return for receiver circuit reference |
| LL | Local Loopback / Quality Detector | A control signal from the DTE to the DCE that causes the analog transmision output to be connected to the analog receiver input. |
| RL | Remote Loopback | Signal from the DTE to the DCE. The local DCE then signals the remote DCE to loopback the analog signal and thus causing a line loopback. |
| SB | Standby Indicator | Signal from the DCE to indicate if it is uses the normal communication or standby channel |
| SC | Send Common | A return signal for transmitter circuit reference |
| SF | Select Frequency | A signal from the DTE to tell the DCE which of the two analog carrier frequencies should be used. |
| SS | Select Standby | A signal from DTE to DCE, to switch between normal communication or standby channel. |
| TM | Test Mode | A signal from the DCE to the DTE that it is in test-mode and can't send any data. |
| Reserved for Testing |
| Contributor: | Joakim Ögren |
| Source: | RS449 Page at Connectivity Knowledge Platform (Made IT) |
Copyright © The Hardware Book Team 1996-2004.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2002-01-13