User's Guide

COMSPHERE 3821Plus Modem
E-2 February 1998 3821-A2-GB20-30
JM8 to RJ11 Crossover Cable
For 2-wire leased-line connections to a JM8 network
interface, an 8-position to 6-position crossover cable (see
Figure E-1) must be used according to the following FCC
requirements:
‘‘The RJ series of jacks should not be used for
connecting data equipment to nonswitched private line
networks – specifically, the service equivalents of the
pre-divestiture Series 3002 (Category II, Tariff #260)
service. There is a substantial difference in transmit levels
permitted in the private line service and those permitted in
the public switched network. The industry standard is now
an 8-pin keyed modular jack known as the USOC JM8
(Bellcore Technical Reference: TR-EOP-000242, Issue 1,
released May 1985.) When ordering the installation of the
USOC JM8, specify the appropriate wiring options:
1. 2-wire operations
2. 4-wire operations w/o TEK leads
3. 4-wire operations with TEK leads
TEK leads are for loopback purposes.
A 50-pin version is being considered for multiple line
connections.”
A JM8 to RJ11 crossover cable may be ordered. See
Appendix G, Equipment List.
Figure E-1. Wiring Diagram — 8-Position to 6-Position Crossover Cable