Modem Signals Description

Modem Signals DescriptionTypes of Modem Signal

The following table describes the various modem signals:

Modem Signal

Description

 

 

Request To Send (RTS)

Asserted by the access server to indicate to

 

the port device that the access server is ready

 

to exchange further control signals with the

 

port device to initiate the exchange of data.

 

The RTS signal is the same state as the DTR

 

signal unless CTS input flow control is

 

enabled.

Clear To Send (CTS)

Monitored by the access server and asserted

 

by the port device to indicate that the port

 

device is ready to receive data.

Data Set Ready (DSR)

Monitored by the access server and asserted

 

by the port device to indicate that the port

 

device is ready to exchange further control

 

signals with the access server.

Data Terminal Ready (DTR)

Asserted by the access server to indicate that

 

the access server is ready to exchange further

 

control signals with the port device to initiate

 

the exchange of data. (DTR is accompanied

 

by RTS and DSRS.)

Data Carrier Detect (DCD)

Monitored by the access server and asserted

 

by the port device to indicate that the received

 

line signal is within acceptable limits.

Speed Mode Indicator (SMI)

Monitored by the access server to detect

 

whether the modem at the access server port

 

has selected the higher or lower speed in its

 

range for exchanging data with a remote

 

modem. SMI allows the use of a primary and

 

alternate (or fallback) speed.

Ring Indicator (RI)

Monitored by the access server. This

 

indicates that a calling signal is being

 

received by the port device.

 

 

Configuring Modem Signals 10-5