Flow Control Guidelines; Transmit Clock Source (Xn) - US Robotics COURIER User Manual

COURIER HIGH SPEED MODEMS
doesn't work, try a fixed link rate of &N6 (9600 bps) or &N3
(2400 bps).
HST modems: We do not recommend synchronous communica-
tions for these modems because of their asymmetrical
modulation, unless you are connecting with another USRobotics
HST modem. In that instance, set both modems to Bl.
For high speed connections with another HST modem, set both
modems to a fixed link rate, &N6 (9600 bps), &NS (14.4K bps), or
&N9 (16.SK bps). Find out first, however, if the Mainframe
accepts link rates over 9600 bps. For 2400-bps connections and
lower, set both modems to a variable link rate, &NO.
Dual Standard modems: Set the Dual Standard modem to BO. Try
a variable link rate setting (&NO) first. If that doesn't work, you
may have to set a fixed link rate, for example, &N6 (9600 bps).
Flow Control
Only the following Courier settings are allowed: &HO or &Hl,
&IO, &RO or &Rl. See Chapter 4 for more information on flow
control settings.
Transmit Clock Source (&Xn)
This setting specifies whether the Courier or your DTE generates
the Transmit clock timing signals for a synchronous call. Most
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users will require the default setting, &XO. -
&XO The Courier is the source of the Transmit clock timing
signals and sends them to your DTE over the RS-232
interface. Default.
&Xl The DTE is the source of the Transmit clock timing signals
and sends them to the Courier over the RS-232 interface.
This setting is used typically in leased line multiplexed
operations. (Multiplexors divide the phone channel so
that the channel carries several calls at the same time.)
We do not recommend this setting for HST modems.
&X2 The Courier's Receiver clock is the source of the timing
signals. The signals are looped to the Transmit clock and
sent to your DTE over the RS-232 interface. This setting is
only used in those systems that require synchronization of
7-4 Synchronous Operations
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