Specifications

11-5
Configuring Modem Signals
Modem Signals Description
Types 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.
Data Signal Rate Selector (DSRS) Asserted by the access server to indicate the speed
at which the modem should initiate
communications. On a port configured for a
multispeed modem (where both SPEED and
ALTERNATE SPEED are specified), DSRS indicates
the higher of the two speeds.