V.32 Bis Mode - US Robotics COURIER User Manual

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COURIER HIGH SPEED MODEMS
2. If set to &N6, &N7, &NS or &N9, the Courier will handshake
at the higher speed, 9600, 12K, 14.4K or 16.SK bps, as shown
in the previous configuration example,
Specialized High-Speed
Connect. However, that configuration example should only
be used in the special situation described, where the system
takes care of error control.
NOTE: Without error control, there are no high speed line
reversals. The high speed channel is always allocated to the
answering modem. Also, there is no online fallback to protect
the connection on impaired lines.
V.32 bis Mode
The handshaking described immediately following this
paragraph adheres precisely to the CCITT recommendation. In
addition, USRobotics V.32
bis modems, when connecting with each
other, use an enhanced proprietary handshaking procedure
which allows them to connect faster and to retrain faster during
calls. They must, however, establish a V.42 error control
connection. This proprietary handshaking is described after the
next section, under
USRobotics V.32 bis to V.32 bis.
V.32 bis
NOTE: High speed calls are highly vulnerable to errors unless
the data is protected by error control. The operations described
below take place even if one of the modems is not set for error
control, thereby prohibiting error control for the call.
Serial port rate: 57.6K/38.4K/19.2K bps
Modem settings: BO, &Bl, &Hl
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&H2/ &H3, &M4/ &MS, &NO
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WARNING: Answering V.32
bis
modems shift their seri"1!
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port rate up to 19.2K bps (for 14.4K bps connections) if the
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calling V.32 bis modem dials at 14.4K or 12K bps. The
answering V.32
bis modem then sends data to its computer at
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19.2K bps. If your computer is limited to a rate of 9600 bps,
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disable high-speed modulation by setting Register S34 to a
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value of 3 (ATS34=3). The calling modem will then shift
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down to 9600 bps for a V.32, not V.32 bis, connection.
1. The answering modem first sends out a 2100 Hz answer tone
identifying it as a V.32 or V.32 bis modem. If the calling
modem recognizes the tone, the modems connect at the
Link Negotiation and Error Control A-3