GE Voluson E Series Service Manual page 150

Components and Functions (Theory)
*) there are 2 variants: RTT/RTH6x (2 boards) or RTH50 only (1 board)
Note
**) there are 2 variants: GES30/RTV30 (2 boards) or GES35 only (1 board)
***) EC320 (BT17) and EC330 (BT18) do not have RSX Extension board
5-4
Figure 5-2 Basic Block diagram of Voluson E-Series
Voluson E-Series Service Manual
5539550APB Revision 6