NEC UX5000 Hardware Manual page 143

Chapter 2 - Blade Installation and Startup
One pair cable
4DIOPU-A1
T(+)
(1) Analog DID Line
R(-)
T
(2) Off-premise extension
R
One pair cable
(Non polarity)
Figure 2-30: DID / OPX POLARITY
The CN2 connector each provides connection to 4 analog DID trunk ports, which are polarity sensitive (tip
to tip, ring to ring). The OPX circuits, however, are not polarity sensitive. The DIOPU requires one universal
slot.
Chapter 2 2 - 63