User Manual

Configuring the traffic interfaces | 111
HSS handshaking and clocking
This section provides detailed information on selecting the recommended handshaking and clocking
modes for the HSS interface card (see "
HSS port settings" on page 109).
HSS handshaking and control line function
HSS X.21 compatibility
In general X.21 usage, the C and I wires function as handshaking lines analogous to RTS/CTS
handshakes. For switched carrier applications, the I wire is used to emulate carrier indications (DCD)
function.
HSS RTS / CTS mode
Set the RTS CTS Mode as required according to the table below. This field controls the state of the
outgoing interface control line.
 When the HSS interface is DCE, the outgoing control line is CTS.
 When the HSS interface is DTE, the outgoing control line is RTS.
RTS CTS
Mode
HSS as a DCE HSS as a DTE Comment
Always Off CTS driven to off state RTS driven to off state
Always On CTS driven to on state RTS driven to on state
Follows
Carrier
CTS follows the state of
the RF link
RTS follows the state of
the RF link
To follow carrier is to
indicate the state of
synchronization of the RF
link
Follows
Carrier +
Remote
RTS/CTS
CTS follows the state of
the RF link and the
remote terminal RTS
input control line if the
remote is a DCE. If the
remote HSS is a DTE,
then CTS follows the
state of the RF link and
the remote HSS CTS
input.
RTS follows the state of
the RF link and the
remote terminal RTS
input control line. The
remote HSS can only
be a DCE.
Control line pass-through
mode where RTS and
CTS are carried over the
link from end to end. The
carrier (as above) plus the
remote terminal input
control line must be
present to output the local
control line signal. The
HSS Control bit in the
Cross Connections
application must be set for
the remote signalling to
operate.
Follows
Carrier +
Remote DCD
CTS follows the state of
the RF link if the remote
HSS is a DCE. If the
remote HSS is a DTE,
then CTS follows the
state of the RF link and
the remote HSS DCD
input control line.
This setting is only
applicable when the local
HSS card in the local
terminal is a DCE. The
HSS Control bit in the
Cross Connections
application must be set for
the remote signalling to
operate.