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COURIER HIGH SPEED MODEMS
Additional Operations G-11
10. Connect the modem's RS-232, power and phone cables, in
that order (see chapter 2). Be sure the phone cable is
plugged into the jack closest to the center of the modem
the jack represented by the wall jack icon on the case bottom
label.
CAUTION: When you power on the modem there will be
potentially hazardous voltage, particularly near the phone
jacks. Do not touch the board when the power is on.
11. Power on the modem. Try MI/MIC closure. Check to see
that the Off Hook (OH) status light goes on. If you dialed a
number, listen for an answer tone from the remote modem.
Then drop the DTR signal. The modem should go on hook
and the OH status light should go off.
12. When you are sure the equipment is working correctly,
disconnect the modem’s RS-232, power and phone cables,
and replace the bottom of the modem case. Ease the two
nibs near the front corners into their openings in the front of
the case top, guide the rectangular slot over the volume
switch, and ease the back of the case bottom into place.
Replace the two screws, the two vinyl feet, and the volume
slide-switch cover.
TROUBLESHOOTING
You may find that the modem does not respond to MI/MIC
closure, which you can monitor by observing the LED. Or the
modem may fail to go back on hook when the computer or
terminal drops the Data Terminal Ready (DTR) signal. The
probable reason for either of these conditions is that your phone
equipment reverses MI/MIC polarity.
It's possible to solve this problem by reversing the modem's
MI/MIC wiring. You'll have to dismantle the modem case
again and reset the two jumper switches on the printed circuit
board, as follows:
1. Lift off the jumpers from J4 and J6. Reverse the positions
shown in Figure G-1. That is, on each switch, cover the
center and rightmost contacts. Make sure the jumpers cover
two contacts on each switch, or you'll disable the MI/MIC
function.