Specifications

Smart Machine Smart Decision
SIM900_AT Commands Manual_V1.07 44 2012.12.10
auto-bauding is enabled. It is recommended to wait 3 to 5 seconds before sending the first AT
character. Otherwise undefined characters might be returned.
If you want to use auto-bauding and auto-answer at the same time, you can easily enable the
DTE-DCE synchronization, when you activate auto-bauding first and then configure the
auto-answer mode.
Restrictions on auto-bauding operation
z The serial interface has to be operated at 8 data bits, no parity and 1 stop bit (factory
setting).
z Only the strings
"AT" or "At" (not "aT" or "at") can be detected when auto-bauding is
enabled.
z AT+IPR=0 setting to auto-bauding will take effect after module resets. If user wants to
change DTE baud rate during module is running, i.e. from 57600 to 4800, DTR shall be
used to urge auto-bauding progress. DTR shall be pulled up to invalid state at least 2
seconds by DTE and then pulled down to valid state. The step will urge auto-bauding
progress and DCE will synchronize its baud rate after it receives data from the serial port.
z Unsolicited Result Codes that may be issued before the ME detects the new baud rate (by
receiving the first AT Command string) will be sent at the previously detected baud rate.
z The Unsolicited Result Codes
"RDY" and so on are not indicated when you start up the ME
while auto-bauding is enabled.
z It is not recommended to switch to auto-bauding from a baud rate that cannot be detected
by the auto-bauding mechanism (e.g. 300 baud). Responses to +IPR=0 and any commands
on the same line might be corrupted.
Auto-bauding and baud rate after restart
The most recently detected baud rate can not be stored when module is powered down.
2.2.42 AT+HVOIC Disconnect Voice Call Only
AT+HVOIC Disconnect Voice Call Only
Execution
Command
AT+HVOIC
Response
Disconnect existing voice call by local TE from Command line and
terminate call with existing PPP or CSD connection on.
OK
Reference
V.25ter
Note