The escape sequence with guard time can be used when the modem is on-line and you need to enter commands to the modem, but you do not want to disconnect from a call. The escape sequence with guard time ensures that the modem connection will not be dropped and no data will be lost while the modem is off-line in the command state.
Because of this patented invention, intelligent modems can provide reliable transmission of data, distinguishing the predetermined escape sequence characters from the random occurrence of like characters in user data.
A guard time must precede and follow the escape sequence to prevent the modem from interpreting similar data (for example, another series of plus (+) characters) as the escape sequence. The default guard time is 1 second.
To enter the escape sequence with guard time, pause a little longer than the guard time, then type:
+++
Then pause again a little longer than the guard time. The guard time pauses before and after the escape sequence, ensure that the modem will distinguish the escape sequence from random user data.
When you receive OK from the modem, which acknowledges that it has "escaped" from the on-line data state, you may enter AT commands.When you are ready to resume your call to a remote system, type:
ATO <CR>
This is the command to return on-line.
The escape sequence character and the guard time interval can be changed by assigning different values to registers S2 (for the escape character) and S12 (for the guard time).
<CR> End-of-line Character
<CR> represents the key on your keyboard that terminates the command line. The key enabling this function is determined by the value stored in S3. The factory setting is ASCII 13, the carriage return character. When the end-of-line character is entered, the modem executes the commands that follow the AT prefix. In this reference, this key is referred to as <CR>. For example, the command line ATV0 <CR> gets the modem's attention, then instructs the modem to display its responses to commands (result codes) as numbers.