CTI Products NCB/IM with Internal PSTN Modem - Manual (Page 53)

CTI Products, Inc. NCB/IM User Guide
Appendix G. Modem Notes 47
parameters and other housekeeping items, and concludes with the "CD" (carrier detect) LED illuminating.
Within 2 seconds after this LED lights, data packets can flow across the modem connection and the
simultaneous voice/data facility is enabled to the “AUDIO” connector.
The elapsed time between training sequence start and end (carrier detect) is tracked by a timer inside each NCB
unit. If the time reaches 20 seconds and training has not concluded, the NCB units will automatically restart the
calling tone sequence. Once a connection is established between the two NCB modems, any loss of carrier will
be detected by both NCB modules and cause them to automatically restart the calling tone sequence. Data
entering the NCB module while the modem is in the calling tone or training sequence is not buffered.
4-wire Leased-Line Wire-color/Connection Method
For actual connection to the telephone circuits in the field, the following table shows typical telephone circuit
connector schemes and functions:
Telco Connector Color / Pins Function Connect to NCB LINE Pins:
42A Block Red & Green
Yellow & Black
Transmit
Receive 3 & 4 (Red & Green)
2 & 5 (Yellow & Black)
66 Block
(Punch Block)
Top-most pair
Bottom-most pair
Transmit
Receive 3 & 4 (Red & Green)
2 & 5 (Yellow & Black)
RJ45 (8 Pin) Pins 1 & 2
Pins 7 & 8 Transmit
Receive 3 & 4 (Red & Green)
2 & 5 (Yellow & Black)
The above data is typical in most situations, but sometimes wire pairs get flipped, causing this information to be
incorrect. If the modem units do not properly communicate after connecting the pairs as above, use the
following procedure to determine proper wire pairs:
1. Disconnect all four wires between both NCB units and their associated telephone circuit wiring.
2. At the site containing the NCB unit in originate mode, connect pins 3 & 4 (Red & Green) from this
NCB to either telephone circuit pair (use the pair you suspect is the transmit pair that carries audio
from the originate mode NCB to the answer mode NCB, if you believe you know which one this is).
3. Be sure this originate mode unit has OPTION 1 switches set correctly (positions 1, 2, 8 DOWN and all
others UP), and that this NCB unit was reset or power-cycled after any switches were changed.
4. At the site containing the NCB unit in answer mode, connect pins 2 & 5 (Yellow & Black) from this
NCB to either telephone circuit pair.
5. Connect a standard telephone handset into the “AUDIO” connector of this answer-mode NCB.
6. Be sure this answer mode unit has OPTION 1 switches set correctly (positions 2 and 8 DOWN and all
others UP), and that this NCB unit was reset or power-cycled after any switches were changed.
7. Listen in the earpiece of the handset for a periodic single tone with about a four second repitition rate.
This is a tone from the originate NCB to the answer NCB.
8. If you hear this tone you have correctly chosen the transmit telephone pair. 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.
9. If you do not hear this periodic tone on the handset connected to the answer-mode NCB, try changing
the connection of pins 2 & 5 (Yellow & Black) of this answer-mode NCB to the other telephone
circuit pair at this site. Reset both NCB units and again listen for the periodic tone in the earpiece of
the handset connected to the answer-mode NCB unit.
10. If step 9 still does not result in a periodic tone in the handset, go back to the site of the originate-mode
NCB unit and change the connection of pins 3 & 4 (Red & Green) of this originate-mode NCB to the
other telephone circuit pair at this site. Reset both NCB units and return to the site of the answer-
mode NCB and listen for the periodic tone.
11. If the actions of step 9 and/or 10 still do not result in a periodic tone in the handset, either the telephone
circuit or the NCB unit(s) must be defective. Have the telephone company installer check the
telephone circuit for proper operation and labeling of the transmit and receive channels at both sites.