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3.0 Modem Setup Options
The Compromise Equalizers option is available for all modes.
NOTE
The compromise equalizers affect only V.32 operation (4800 to 14,400
bps, asynchronous/synchronous, full duplex).
For most applications, the automatic adaptive equalizer setting provides all
the equalization necessary to compensate for line impairments, meaning that
equalizer adjustments are generally not necessary. However, in the event that
equalizer adjustment is needed, any of four types of compromise equalization
can be selected: Type I (T-I on the LCD), Type II (T-II), Type III (T-III) and
Type IV (T-IV). The equalizer can also be turned OFF.
Where line conditions are atypical, it may be necessary to adjust the equalizers
to optimize the signal quality. If adjustment is necessary, refer to the quality
screen for guidance; this screen shows a relative indication of the signal
quality, in both numeric and graphic form.
The Trellis Code option is available for all modes. Trellis coding provides
performance advantages for all modulation patterns. The modem’s CCITT
compliant trellis coder is normally enabled at speeds of 9600 bps and above,
but may be negotiated off by a modem that is not equipped with a trellis
coder. The trellis code option allows you to enable or disable the trellis coder.
The Transmitter Clocking option is available for all modes. It selects one of
three possible sources for the transmitter timing signal:
• INTERNAL — The timing of the modem and data terminal transmitting
circuits is provided by an internal clock within the modem.
• RECEIVED (RX-CLK) — The timing of the received data is used to
control the timing of the data transmitted. This timing mode is used if the
modem’s transmit timing must be controlled by a remote source.
• EXTERNAL — The timing of the modem and data terminal transmitting
circuits is provided by an external clock within the data terminal and is
provided to the modem via the DTE connector pin 24. This mode of
clocking is used if the DTE must be in control of the modem’s transmit
timing.
The T1 Timer option is available for Hayes, V.25 bis, and Dumb modes. It
determines how long the Modem attempts to handshake with a calling V.32
modem before falling back to a lower speed. The available T1 Timer settings
are 0, 0.3, 0.8, 1.6 and 3.0 seconds.