What is the difference between the WA-TX-03-R,WA-RX-03-R and WA-TX-03S,WA-RX-03S?

The WA-TX-03S, WA-RX-03S has the additional feature of 2 RF power selections (5 mW or 10mW). This is performed by applying a signal to the RF Power Selection pin. Functionally and physically it is the same as the WA-TX-03-R, WA-RX-03-R.