Many modems will report the status of the call as a string. These strings may be CONNECTED or NO CARRIER or BUSY. It is often desirable to terminate the script should the modem fail to connect to the remote. The difficulty is that a script would not know exactly which modem string it may receive. On one attempt, it may receive BUSY while the next time it may receive NO CARRIER.
These "abort" strings may be specified in the script using the ABORT sequence. It is written in the script as in the following example:
"ABORT" , "BUSY" ,
"ABORT" , "NO CARRIER" ,
"" , "ATZ" ,
"OK" , "ATDT5551212" ,
"CONNECT" , ...
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This sequence will expect nothing; and then send the string ATZ. The expected response to this is the string OK. When it receives OK, it sends the string ATDT5551212 to dial the telephone. The expected string is CONNECT. If the string CONNECT is received the remainder of the script is executed. However, should the modem find a busy telephone, it will send the string BUSY. This will cause the string to match the abort character sequence. The script will then fail because it found a match to the abort string. If it received the string NO CARRIER, it will abort for the same reason. Either string may be received. Either string will terminate the chat script.