User's Guide Modem 56

Page 148
AT#V Verifier
The #V command selects whether your modem will check the validity of the commands you
issue to it.
Your modem can check both AT commands and values you write to the S Registers.
When you use the #V0 command, no checking is performed on commands you issue. If you
issue an unsupported command, the modem responds with an OK message.
With #V1 selected, if you attempt to issue an invalid command or read or write to a reserved S
Register, the modem will return an ERROR message.
☞☞
☞☞
☞ If you issue an AT command string containing multiple commands, and one has
incorrect syntax then none of the commands in the line will be executed
Options
AT#V0 Command and S Register verifier off
AT#V1■ Command and S Register verifier on
Range
0-1