# Acknowledge Signal

Once the vision system receives a run time command (such as LF, GP commands) from an external device, it will generate a Token for that command and send it back to the external device in the form of a string. The string format is merely one parameter: Token, followed by CR/LF.

## Token

A token is a unique number automatically generated by an AlignPlus program as a response for a received command. The same token will be returned in the result string again when the requested tasks finish execution. Therefore, the external device can use the token to match the result string with the command it sent out. This is especially important when the sequence of received result strings are not the same with the sequence of their corresponding sent-out commands due to running in the asynchronous mode.