This attribute specifies the line signals originating from the V.35
interface that will always be turned on, provided the interface passes
its diagnostics. This set of signals is generally required for
maintaining the connection. Note that both DTE and DCE signals
are specified in this attribute. The appropriate set of specified
signals will be turned on or checked according to the
actualLinkMode.
See also linkMode.
Description of bits:
rfs(0)
dsr(1)
dcd(2)
rts(3)