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Quantum and Evolution Series Installation and Operating Handbook
Min
Signal Description
Req
Device (DTE) Ready In
Device (DCE) Ready Out
Local Loop In
Remote Loop In
The modem can operate at high data rates using the LVDS interface, but the maximum
useable data rate is limited by 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. 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).
The input clock/data phase is selected automatically, reporting a `Data Marginal` warning
whenever it has to switch phase. If the modem reports Data Marginal frequently then this is
not a modem fault but an indication that you have a clocking problem external to the
modem (ie changing clock/data phase, a problem which would otherwise have caused
untraceable data errors). With the Tx Clocking Set to Tx Clock In the `Data In` signal is
checked against the `Clock In` signal. With the Tx Clocking Set to Internal or Rx the `Data
In` signal is checked against the `Int` Tx Clk Out` signal.
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, RTS enabled.
Q3705 in HSSI Mode
If the HSSI interface is fitted and is selected under Edit/Unit/Interface/Terrestrial then the
following interface description applies.
Min
Signal Description
Req
DATA CIRCUIT TOWARDS MODEM (TX)
Clock In
Data In
Signal Ground
DTE Available
'
Int
Tx Clock Out
DATA CIRCUIT FROM MODEM (RX)
LVDS
Circuit
25 pin
Name
Number
TR
108
20
DM
107
6
LL
141
18
RL
140
21
HSSI
50 pin
Name
+
TT
9
SD
11
SG
7
TA
8
ST
6
10-3
Electrical
Levels
23
LVDS
22
LVDS
LVDS
LVDS
Electrical
Levels
-
34
ECL
36
ECL
32
Ground
33
ECL
31
ECL
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