RFL SMX3 / 21
Page 12 of 22
Issue 1.4
User Manual
08 June 2009
V.24 Data Channel Concatenation
SMX3/21 units co-located at one end of adjacent unsynchronised links may be
concatenated at the V.24 level either through the connected equipment, or directly
using a crossed RS232 data cable.
V.24 Port Performance
V.24 circuits operate to emulate a modem:
CTS follows the state of local RTS after any necessary delay, when the
Aggregate is working and in synchronism.
DCD follows the state of remote RTS when the Aggregate is working and in
synchronism.
DTR is ignored and can be left unconnected, the sub-multiplexer assumes a
continuous ON state.
DSR is ON when the Aggregate is working an in synchronism.
RI is unconnected or permanently OFF.
When RTS turns ON, CTS turns ON when it can be assured that data presented at
TxD will reach RxD at a remote end after DCD there has turned ON. This does not
exceed 10 ms.
It is possible to configure each port to limit the duration of the effect of RTS to protect
a SCADA system from an RTU which fails to turn RTS off after it has sent a
response. When enabled, by DIP switch (SW 6-1 and 6-2), if RTS remains ON for
longer than 2 seconds, its effect is terminated and its ON condition is not recognised
again until it has been OFF for longer than 2 seconds.
