[arm-allstar] Transmit A Question

[Chris Souleles]

A couple questions trying to understand how things work and how to make adjustments.  My node is RPI3, DMK URi and BF888.  
What is actually being changed when I adjust the Transmit A level in simpleusb?  I assume this is not actually changing the RF power level of the radio in the node.  Is this the level being transmitted from the radio to the radio/usb interface?  I don't notice much difference when I change this setting.
Also is Transmit B level only used if I have a second radio in the node.  Right now I have it set to zero and everything seems to be working.
Thanks,  Chris - W6CS - 73