The ACU knows a number of parameters, each identified by a parameter name. To set a certain parameter to a new value, a message:

name=value

has to be sent to the ACU. The ACU interprets this command, checks the range of value , sets the internal parameter and then answers:

name=value

The value in the reply is the value actually recognized by the ACU. For instance, if the requested value was out of range, the replied (and internally used) value is limited to the applicable minimum or maximum.

To read a parameter from the ACU, instead of a new parameter value a question mark is sent:

name=?

The ACU replies the actual value in a complete message:

name=value

A complete list of the parameter the ACU knows is shown later in this document in chapter Parameter list . Below, some common rules applying to the remote control message syntax are summarized.

• Parameter names always are of lower case letters, most of them are four characters long.
• Non-numeric parameter values always are written in upper case.
• Numeric (floating point) values may be specified with an arbitrary precision, however the device will reply only a fixed number of places. The ACU recognizes a decimal point (‘.’), numbers must not contain any commas.
• There must not be any whitespace in front or after the ‘=’ in a message.
• If the command/query is not of the form name=value or name=? , the ACU replies the message ?SYNTAX .
• If the message syntax is OK, but contains an unknown parameter name is used, the reply is ?UNKNOWN
• Numeric parameters are cut to the limits defined for this particular parameter.
• Misspelled choice values cause the ACU to set the first value of the choice list.
• Assigning a value to a read-only parameter will cause no fault, however the ACU will overwrite this parameter immediately or some seconds later with the actual value.