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P300H P300 Series Modem Installation and Operating Handbook Page 169
P1440 IN V.35 MODE
The P1440 is the standard interface supplied with the P300 Series Modem. If V.35 is selected under
Change, Terr-Intfc, Electrical then the following interface description applies.
Min V.35 Circuit Electrical Old Style
Req Name Number Levels Winchester
Signal Description
25 pin 37 pin
ABAB
DATA CIRCUIT TOWARDS MODEM (TX)
Clock In SCTE 113 24111735 V.35 U & W
Data In SD 103 2 14 4 22 V.35 P & S
Sig’ Valid In RTS 105 4 7 RS232 C
Sig Accpt’d Out CTS 106 5 9 RS232 D
Int’ Tx Clock Out SCT 114 15 12 5 23 V.35 Y & aa
DATA CIRCUIT FROM MODEM (RX)
Clock Out SCR 115 17 9 8 26 V.35 V & X
Data Out RD 104 3 16 6 24 V.35 R & T
Sig’ Valid Out RLSD 109 8 13 RS232 F
COMMON LINES
Signal Ground SG 102 7 19, 20, 21 Ground B
Shield/Protective ground FG 101 1 1 Screen A
Device (DTE) Ready In DTR 108 20 12 RS232 H
Device (DCE) Ready Out DSR 107 6 11 RS232
E
Local Loop In LL 141 18 10 RS232 -
Remote Loop In RL 140 21 14 RS232 -
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). 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.
Note that although there are both 25 pin EIA530 pinout and 37 pin RS449 pinout connectors on the rear
panel, these are simply connected in parallel. Do not use both connectors at the same time. If you
require the older 34 pin `Winchester` connector then an adaptor lead is required, please contact the factory
for details.
By selecting Change, Terr-Intfc, Control Lines it is possible to configure the modem to raise an alarm if
either the `Sig’ Valid In` line (RTS) or `Device (DTE) Ready In` line (DTR) 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 (RTS) by
selecting Change, Tx, Modulator, Carrier, RTS-Controlled.