Polycom SoundStructure C16 Design Manual page 369

Acknowledgements are generated when either a parameter command is
issued or a parameter changes value for some other reason. When a parameter
command is executed with the get action, the acknowledgement is only sent to
the control interface that the parameter command was received from.
When a parameter command is executed with the get action, the acknowledgement
is only sent to the control interface that the parameter command was received from.
Warning
When a parameter command is executed with the set, inc, dec, or tog actions,
then if the action results in the parameter changing value, the
acknowledgement is sent to all control interfaces on all devices, otherwise (if
the action doesn't change the value of the parameter) the acknowledgement is
sent only to the control interface that the parameter command was received
on. When a parameter changes state for any reason (for example, command
execution, logic pin operations, etc.) an acknowledgement is sent to all
interfaces on all devices.
As an example, consider the fader command, and assume a Mic Input mono
virtual channel has been defined with the label "Microphone 1". Also assume
the current value of the fader parameter for that channel is 3. If a control
program connected to any control interface of the SoundStructure device
sends the following command:
set fader "Microphone 1" 6.0
then the following acknowledgement will be generated,
val fader "Microphone 1" 6.0
This acknowledgement will be sent to all control interfaces on all
SoundStructure devices. Now, if the control program sends this command:
get fader "Microphone 1"
then the following acknowledgement will be generated,
val fader "Microphone 1" 6.0
but this acknowledgement will only be sent to the specific device and control
interface that the control program is communicating through.
This implementation of the command protocol has been designed with these
frugal acknowledgments because some control systems have limited buffer
sizes that are susceptible to buffer overflows when large amounts of data
traffic are generated that the particular control port didn't request.
Command Protocol Reference Guide
A - 27