Description

Circuit

Function

Shield Ground

AA

This is the chassis ground connection between the DTE and the DCE. It is also referred to as 'protective ground'.

Signal Ground

AB

This is the reference ground (0 V DC) between the DTE and the DCE.

Transmitted Data

BA

These are the data sent by the DTE.

Received Data

BB

These are the data received by the DTE.

Request To Send

CA

This is a signal generated by the DTE to start the transmission of the DCE.

Clear To Send

CB

This is a signal sent by the DCE as a reply to the RTS signal and used to provide the DCE with enough time to prepare.

DCE Ready

CC

Also known as the DSR, this signal is generated by the DCE to indicate that it is operational.

DTE Ready

CD

Also known as the DTR, this signal is generated by the DTE to instruct the DCE to setup a connection, thereby indicating as well that the DTE is ready to communicate.

Ring Indicator

CE

This is a signal from the DCE to the DTE that the telephone is ringing (there is an incoming call.  This is only used on switched circuit connections.

Received Line Signal Detector

CF

Also known as DCD, this is a signal sent from the DCE to the  DTE to indicate that it has received a basic carrier signal from a remote DCE.

Data Signal Rate Select

CH/CI

This is a control signal used for changing the transmission speed.

Transmit Signal Element Timing

DA

These are timing signals used by the DTE for transmission, wherein the clock is provided by the DTE and the DCE acts as its slave.

Transmitter Signal Element Timing

DB

These are  timing signals also used by the DTE for transmission.

Receiver Signal Element Timing

DD

These are timing signals used by the DTE when receiving data.

Remote Loopback

RL/CG

This is a signal generated by the DCE that changes state when the analog signal received from the (remote) DCE becomes marginal.