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P300H P300 Series Modem Installation and Operating Handbook Page 170
P1440 IN RS232 MODE
The P1440 is the standard interface supplied with the P300 Series Modem. If RS232 is selected under
Change, Terr-Intfc, Electrical then the following interface description applies.
Min RS232 Circuit Electrical
Req Name Number Levels
Signal Description
25 pin 37 pin
ABAB
DATA CIRCUIT TOWARDS MODEM (TX)
Clock In DA 113 24 17 RS232
Data In BA 103 2 4 RS232
Sig’ Valid In CA 105 4 7 RS232
Sig Accpt’d Out CB 106 5 9 RS232
Int’ Tx Clock Out DB 114 15 5 RS232
DATA CIRCUIT FROM MODEM (RX)
Clock Out DD 115 17 8 RS232
Data Out BB 104 3 6 RS232
Sig’ Valid Out CF 109 8 13 RS232
COMMON LINES
Signal Ground AB 102 7 19, 20, 21 Ground
Shield/Protective ground SHIELD 101 1 1 Screen
Device (DTE) Ready In CD 108 20 12 RS232
Device (DCE) Ready Out CC 107 6 11 RS232
Local Loop In LL 141 18 10 RS232
Remote Loop In RL 140 21 14 RS232
The maximum data rate is 100kbps (over good quality 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 50kbps to 20m, 25kbps to 40m etc). NOTE this is a synchronous RS232 interface, if you need
an asynchronous interface, please contact the factory.
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. The EIA530
connector is pin compatible with the standard 25 pin RS232 interface.
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 (CA) or `Device (DTE) Ready In` line (CD) 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 (CA) by selecting
Change, Tx, Modulator, Carrier, RTS-Controlled.