Nmdu And Ndcu - Toshiba Perfecptione Installation And Maintenance Manual

INSTALLATION INSTRUCTIONS
SECTION 200-255-204
FEBRUARY1992
Loop/Ground Start Mode
7) In some installations, particularly those near
the serving Central Office, noise may be intro-
duced over the CO trunk that will appear as
sidetone at the telephone. In such situations,
a 2dB pad can be inserted into the line, for
either incoming voice or outgoing voice, to
reduce the sidetone. Strapping options for the
2dB pad are shown below.
8) Install the NDTU in the TOO slot in the main
cabinet. If applicable, install a second NDTU
in the TO8 slot. Connect the NDTU to the CSU
using the Toshiba-supplied cable.
9) The NDTU contains an on-board 12.288 MHz
clock used to synchronize the NDTU with the
NTWU-3. Connect a coaxial clock cable from
NDTU connector 53 to NTWU connector J2.
3.90 NMDU and NDCU
3.91 The NMDU (Figure 4-22) must be strapped
for operation with either a one-pair or two-pair
modem connection. The two strapping positions for
each modem are shown below.
CIRCUIT
OPEfi
STRAPS
One-pair
4
TB
501
I
I
1 TB 502 1
,TION
Two-pair
A-B
3.92 To change the strap positions on TB 8011802
it is necessary to lift the small piggy-back PCB off
the NMDU. Replace the PCB once the straps have
been changed.
3.93 If any of the first four NMDU circuits are not
used for Modem Pooling, the corresponding DDIU
4-18