The physical layer of this protocol is variable and the user is responsible for making sure that an appropriate standard (RS-232, RS-422, RS-485, etc.) is used. Conversion devices to interface to these standards are readily available.
The commands have a relatively simple format. Each command is identified by an ASCII character. Commands that require a numeric value will transmit the ASCII representation of that value in front of the command identifier. Last of all, each command is followed by a lower case “a”.