RTS stands for Request To Send, it is a control lead presented
by the DTE (Data Terminal Equipment) to indicate that it has data
that it would like to transmit. The Verilink IDCSU is DCE
(Data Communications Equipment) which expects to receive RTS as an
input from the DTE (Data Terminal Equipment). Typically if RTS is not
asserted by the DTE then no user data is conveyed end to end.
If the DTE does not assert RTS this option allows the IDCSU
to behave as it would if RTS were asserted by the DTE. The IDCSU will
output CTS (Clear To Send) as a HIGH or asserted value when RTS is on.