EIA-449 (RS-449)

Common names: EIA-449, RS-449, ISO 4902
Primary channel

37 PIN D-SUB MALE (at the DTE)
37 PIN D-SUB FEMALE (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)