Paradise Datacom P300 Series Installation & Operating Handbook page 177

X.21 DTE OPERATION
This only has a clock to the modem from the terrestrial equipment. Configure a cable with a 15 pin `D`
male at one end (X.21 DTE) and either a 25 pin or 37 pin `D` male (not both) at the other end as follows:
Min X.21 DTE
Req
(15 pin D male)
Name A
DATA CIRCUIT TOWARDS MODEM (TX)
S 6
R 4
I 5
DATA CIRCUIT FROM MODEM (RX)
T 2
C 3
COMMON LINES
Sig gnd 8
Prot gnd 1
Clocking: IMPORTANT
The interface will not work as X.21 unless you set the clocking correctly! The Tx Clocking menu should
be set take the single clock from the terrestrial by selecting
be set to return Rx data in time with the single Tx Clock by also selecting
COMBINATIONS WILL WORK.
The maximum data rate is 10Mbps (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 (ie 5Mbps to 20m, 2.5Mbps to 40m etc).
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). Check the phase of the Data In
with respect to the Clock In line.
By selecting ,
either the `Sig` Valid In` line (I) switches to the inactive state. As there is no X.21 equivalent of the
RS422 `Device (DTE) Ready In` line (TR), set this to
carrier to be switched on and off by the `Sig` Valid In` line (I) by selecting
, .
P300H P300 Series Modem Installation and Operating Handbook
Signal RS422
Description Name
B
13 Clock In TT
11 SD
Data In
`
Sig Valid In
12 RS
9 Data Out RD
`
10 Sig Valid Out RR
Signal Ground SG
`
Shield / Prot PG
ground
, it is possible to configure the modem to raise an alarm if
Circuit 25 pin
Number
A B A
113 24 11 17
103 2 14 4
105 4 19 7
104 3 16 6
109 8 10 13
102 7 19, 20, 21
101 1
The Rx Clock menu should also
. It is also possible to configure the Tx
37 pin Electrical
Levels
B
35 RS422
22 RS422
25 RS422
24 RS422
31 RS422
Ground
1 Screen
. NO OTHER
, , ,
Page 177