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Modem Signals Description
Modem Signals DescriptionTypes of Modem SignalThe 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