Reference Manual V1.19    Software Versions 4.xx 
003R-682-119  Page 13 
Long Ring Network: Multiple Instruments to PC (RXD, TXD, GND) 
The Long Ring Network layout can be used in situations where each leg of the cable run 
can be up to about 150 m (500 ft.) at 9600 baud. If there are communications errors, 
lower the baud rate to 4800 or 2400. 
 
Figure 8: RS-232 Long Cable Runs: Ring Network using COM Port (DB9)