User's Manual

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5.12.3.4 Data Terminal Ready (DTR1)
DTR indicates that the DTE is ready to receive data. It also acts as a hardware ‘hang-
up’, terminating calls when switched high. The signal is active low. Users can define
the exact behavior of DTR with an the AT&D command. DTR1 is used as an optional
sleep control mechanism when the module is configured appropriately.
5.12.3.5 Data Set Ready (DSR1)
DSR indicates that the DCE is ready to receive data. The signal is active low. Behavior
is controlled using the AT&S command. DSR1 is used as an optional sleep control
mechanism when the module is configured appropriately
5.12.3.6 Data Carrier Detect (DCD1)
DCD indicates that the DCE is receiving a valid carrier (data signal) when low.
Behavior is controlled using the AT&C command.
5.12.3.7 Ring Indicator (RI)
RI indicates that a ringing signal is being received by the DCE when toggled low.
Users can define the exact behavior of RI with an AT command, including the option
of asserting the RI signal to flag an incoming SMS by using the AT*E2SMSRI
command.