US Robotics COURIER - Page 171

COURIER HIGH SPEED MODEMS
Ml/MIC OPERATIONS
DESCRIPTION
Mode Indicate/Mode Indicate Common (Ml/MIC) closure is
required by some installations whose existing hardware does the
dialing. The modems do not Auto Dial.
In these situations, the modem must be forced off hook in
Originate mode. This is done by shorting (closing) two of the
pins (not Tip and Ring) in the phone connector. The modem is
then ready to go online and accept data when it connects with
the number dialed by the system equipment.
Courier modems are shipped with Ml/MIC disabled, that is, for
normal use. To set the modems for Ml/MIC closure, enable bit 5
of Register 534: AT534=32 or AT534 .5=1. We recommend that
you write that setting to NVRAM as a power-on default.
Once you've set Register 534, have the system force the modem
off hook by closing the Ml/MIC leads in the phone line
connector. The modem's OH (Off Hook) status light, or LED,
goes on when the modem goes off hook.
TROUBLESHOOTING
You may find that the modem does not respond to Ml/MIC
closure, which you can monitor by observing the LED. Or the
modem may fail to go back on hook when the DTE drops the
Data Terminal Ready (DTR) signal. The probable reason for
either of these conditions is that your phone equipment reverses
Ml/MIC polarity.
It's possible to solve this problem by reversing the modem's
Ml/MIC wiring. You'll have to dismantle the modem case and
reset two switches on the printed circuit board, as follows.
1. Power off the modem and disconnect all of its cables.
2. Turn the modem upside down. Remove the two square
vinyl feet near the back of the case, on either side of the
bottom label's DIP switch diagram. Be careful to put the
vinyl feet aside, upside down, where they won't become
stuck to another object.
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3. Remove the two Phillips screws located in the wells beneath -
the vinyl feet.
E-20 Fax and Other Operations
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