Q-Flex Satellite Modem Installation and Operating Handbook
9-3
By selecting
Advanced
it is possible to configure the modem to raise an alarm if either the
`Sig` Valid In` line (RS) or `Device (DTE) Ready In` line (TR) switch to the inactive state. It
is also possible to configure the Tx carrier to be switched on and off by the `Sig` Valid In`
line (RS) by selecting
Edit->Tx->Carrier
and selecting
RTS enabled
.
Q3705 HSSI Interface
The HSSI interface is used as follows.
Min
Req
Signal Description
HSSI
Name
50 pin
Electrical
Levels
+
-
DATA CIRCUIT TOWARDS MODEM (TX)
Clock In
TT
9
34
ECL
Data In
SD
11
36
ECL
Signal Ground
SG
7
32
Ground
DTE Available
TA
8
33
ECL
Int
’
Tx Clock Out
ST
6
31
ECL
DATA CIRCUIT FROM MODEM (RX)
Clock Out
RT
2
27
ECL
Data Out
RD
4
29
ECL
Signal Ground
SG
1
26
Ground
DCE Available
CA
3
28
ECL
COMMON LINES
Signal Ground
SG
13
38
Ground
Signal Ground
SG
19
44
Ground
Loopback Circuit A
LA
10
35
ECL
Loopback Circuit B
LB
12
37
ECL
Loopback Circuit C
LC
5
30
ECL
The modem can operate at high data rates using the HSSI interface, but the maximum
useable data rate is limited by the connecting cable length. The maximum data rate
is
10Mbps over a 10m cable (over good quality twisted pair screened cable), but this rate is
reduced as the connecting cables extend beyond 10m. As an estimate, assume the
maximum rate halves as the distance doubles (e.g. 5Mbps to 20m, 2.5Mbps to 40m, etc).
Similarly, the maximum data rate increases as the connecting cable length is reduced (i.e.
20Mbps to 5m, 40Mbps to 2.5m).