CTI Products NCB/IM with Internal PSTN Modem - Manual (Page 54)

CTI Products, Inc. NCB/IM User Guide
Appendix G. Modem Notes 48
12. If the actions of step 9 or 10 do result in a periodic tone, proceed by connnecting the remaining pair
from each NCB unit to each remaining telephone circuit pair at each site. Reset both NCB units (or
wait for them to timeout and recycle, approximately 60 seconds) and they should complete the modem
training process and turn on their “CD” LEDs within 30 seconds.
See text in section “2.
S ETUP AND O PERATION
”, “S
TEP 3. E LECTRICAL C ONNECTIONS
”
for important information
when connecting two NCB units “back-to-back” in Leased-Line mode with a short phone cable.
Certain leased-line audio circuits (most notably microwave RF channels) provide a 4-wire circuit made up of a
Transmit pair and a Receive pair. Use the 4-Wire mode in these situations. Be sure to provide proper wiring in
4-Wire mode.