NI-USRP properties can be applied to the session, device, or channel.
When a property is applied to the session, you can set only a single value for this property, and that value applies to all devices in the session. When a property is applied to the channel or device, there may be multiple values for the property (one for each separate channel or device).
When you set a property, use the Active Channel property in niUSRP Properties to specify the device or channel to which the value applies. When you pass NULL or the empty string ("") for this parameter, and the property applies to multiple channels or devices, NI-USRP attempts to set the value on all valid channels or devices.