CTI Products NCB/EM with External PSTN Modem User Manual
Page 18
CTI Products, Inc.
NCB-EM User Guide
2. Setup and Operation
12
Dial-Up Modems
A dial-up connection uses a 2-wire connection scheme to a standard telephone circuit. A standard telephone
cord can be used.
Leased-Line Modems
A leased-line connection can use either a 2-wire or 4-wire scheme to a dedicated leased-line circuit:
2-Wire Leased-Line
In 2-wire Leased-Line mode, the audio circuit must pass audio simultaneously in both directions. For this
mode, use pins 3 & 4 (red and green) of the “LEASE/PRIVATE” connector. Pins 2 and 5 are unused in 2-wire
mode.
For testing “on the bench” in 2-wire Leased-Line mode, two modems may be connected “back-to-back” using
the standard modular telephone cable provided with each modem. For this short cable back-to-back
connection, however, MODEM DIP Switch 3 must be placed in the UP position (followed by resetting the
NCB unit) on BOTH NCB units. This lowers the transmit level to prevent clipping of the signal due to the
short (near lossless) cable. Be sure to return MODEM DIP Switch 3 to the DOWN position before installing
the modem in the field. (Leased-Line modems designed for use in the United Kingdom will require a cable that
uses the outer 2 pins of a 6-pin RJ11 connector.)
4-Wire Leased-Line
In 4-wire Leased-Line mode, two pairs are used, one for Transmitting to the other
NCB and one for Receiving from the other NCB. For this mode, pins 3 & 4 (red
and green) of the “LEASE/PRIVATE” connector carries ‘transmit audio’ from
this unit to the other unit and pins 2 & 5 (black and yellow) carries ‘receive audio’
to this unit from the other unit. A 4-wire leased-line telephone circuit has two
channels and each channel carries audio in only one direction.
For testing “on the bench” in 4-wire Leased-Line mode, two NCB units with
modems must be connected “back-to-back” by connecting the transmit pair of each unit to the receive pair of
the opposite unit. This cannot be done with the telephone cable having modular connectors on both ends, as
this cable is wired “straight through”. Instead, use the modular plug to spade lug cables provided. Also, for this
short cable back-to-back connection, MODEM DIP Switch 3 must be placed in the UP position on BOTH
modems (followed by resetting the modems). This lowers the transmit level to prevent clipping of the signal
due to the short (near lossless) cable. Be sure to return MODEM DIP Switch 3 to the DOWN position before
installing the modem in the field.
DC Power Connection
DC power must be attached to the NCB module via the DC IN connector (see
“A
”). Apply DC power to the NCB module
only after all other connections have been made. A wall plug-in style power
supply designed for the NCB module is an available option.
for 4-Wire
Leased-Line
pinouts and wire
colors.
DC IN