ATS5=27 designates ESC as the backspace character.
3.6Modem AT Response Codes
Unless you have instructed the modem not to send response codes by issuing command Q1, it will always send a response code after executing a command line. The response code can be displayed in word or in digit form depending on the V command issued.
Command X0 to X4 lets you select different response sets of the modem, which enables or disables certain response codes. In general application, you can select X4, the default, which enables all response codes so that the most specific response message can be displayed. If you plan to write your own software for special applications, you may select the response set you require by issuing an appropriate X command.
The following table shows the response codes from 0 to 8 related to each command. The means the response code is disabled for the corresponding command. The remaining response codes are enabled.
Page: 18