Iwatsu VOAC760 Manual page 33

(Example) : VOLT:AC:NULL ON;:VOLT:AC:BAND 20
The above message can be written in the following format.
: VOLT:AC:NULL ON;BAND 20
(If the parent command is omitted, care should be taken so that the colon (:) is not
put in the header part.) This function specifies the parent command :VOLT:AC as
the header path.
The header path designation is valid only within the message (until the delimiter). In the next message,
the parent command of the start message unit is specified as a header path. Therefore, if the colon (:)
for the first character of the header part is omitted at the top of the message, the message is
determined as parent command.
(Example) : VOLT:AC:NULL ON
The above message can be written in the following format.
: VOLT:AC:NULL ON
If "VOLT:AC:NULL ON;BAND 20" is sent as one message, it is interrupted correctly.
However, ":VOLT:AC:NULL ON;BAND 20" is sent with it separated into "VOLT:AC:NULL ON" and
"BAND 3," it is determined as an error.
(This instrument does not have the BAND parent command.)
If the message is started with a colon (:), this command is determined as a parent command. The
header path is also updated and this command becomes a new header path.
(Example) : VOLT:AC:NULL ON;BAND 20;:VOLT:DC:NULL ON;NPLC 1
The header path is VOLT:AC:. The header path is VOLT:DC.
This instrument does not perform command retrieval by going upstream command tree. Therefore in
the case a message unit of different parent commands is to be one message, please always start by
putting colon (:) at the head of message unit to be header path switched.
(Example) : VOLT:AC:NULL ON;BAND 20;:VOLT:DC:NULL ON;NPLC 1
The above header path rules do not apply to the common commands (  WAI,  OPC, etc.) defined in
IEEE488.2.
The common commands are executed with the header path omitted. However, the header path
destination is not broken and the previous header path is valid when interpreting the next message
unit after the common command.
(Example) : VOLT:AC:NULL ON;
↑
↑
This part cannot be omitted.

WAI;BAND 20
19
↑
The header path is VOLT:AC.
The common command  WAI is executed
correctly.