Nortel Passport 15000, Hardware Installation And Maintenance, Page: 551 / 874

Chapter 17 Hardware procedures 551
Passport 15000, 20000 Hardware Installation, Maintenance, and Upgrade 5.2S2
Installing a timing cable adaptor NTPN81
Install a balanced-to-unbalanced timing cable adaptor (NTPN81) to convert
an E1 alarm/BITS module into an unbalanced version on Passport 20000.
Prerequisites
• You must be familiar with “Safety considerations and best practices”
(page 53).
• You need a hardware kit with PEC NTPN81. The kit provides a cable
assembly and a balun adapter to convert an NTPN13 alarm/BITS module
into an unbalanced version. For a redundant timing configuration, two
kits are required. The kit includes:
— a 38-cm (15-in.) E1 timing cable assembly with a DB-9 connector at
one end and an RJ-45 at the other
— a balun adapter unit, G.703 model 460 series manufactured by
Patton Electronics Co.
• The cable assembly and the adapter provide a balanced-to-unbalanced
coax-to-twisted-pair connection. The cable allows 75-ohm coax
hardware to communicate with 120-ohm twisted pair hardware through
standard unshielded category 3 cable. See the figure “A timing cable
assembly from kit NTPN81” (page 553) and the figures in the User
Manual provided with the 460.
• The cable assembly NTPN81 does not require EMI filters on the J3 or J4
connections.
• The balun cable connection is designed for common bond grounding.
The cable is always grounded on a Passport 15000 or 20000 unless you
alter it for the receive (Rx) end of the connection. The transmit (Tx) end
of the connection is ungrounded for a Passport 15000 or 20000 because
that connection is unused. When you choose to not ground the timing
cable, jumper JP2 must be removed to break the shield connection. The
instructions to remove it are included in the User Manual of the model
460.