[Tinyos-help] question about ADG715 switch on TelosB

[UGlee]

I know that the question is not related to tinyos but I could not find
anywhere else to seek the answer.

1) I noticed there is a ADG715 switch IC on telosB board. What's it
for? I also noticed on similar hardware, the epic mote, there is no
'switch ic' on either dev board or miniprog board. So, what is the
benift of using switch ic instead of directly connecting FT232 to
MSP430 tck/rst/uart.
2) In telosb design, besides connecting FT232 to MSP430, ADG715 also
has the following connection:

FT232
DCO <-> TDO
RI <-> TDI
DSR <-> TMS
DTR <-> TCK

Could anyone briefly introduce the logic or ADG715 on telosb design? I
am really confused.

Thanks in advance.

UGlee