Cabletron Systems THN-MIM - Manual (Page 11)

INSTALLATION
Page 2-2
Since the ports on the module are internally terminated, the end of
the segment that will be connected to the module will not be a tee
connector or terminator.
2.2.2 Thin-net Segments (THN-MIM7593 only)
The following network design guideline must be followed when
connecting 75 or 93 ohm coaxial cable segments to the THN-MIM7593.
If not, unsatisfactory network performance may result.
• The length of the 75 or 93 ohm coaxial cable segment is dependent
on signal loss from one end of the cable segment to the other. Signal
loss must not exceed 4 db when measured with a 5 MHz sine wave
or 6.5 db when measured with a 10 MHz sine wave.
• A 75 or 93 ohm coaxial cable segment will only support point to
point communication, from one Ethernet device to the
THN-MIM7593. No other Ethernet devices are allowed on the
segment.
• The far end of the 75 or 93 ohm coaxial cable segment must be
terminated with a 50 ohm terminator. This will ensure that the
Ethernet device on the segment will receive the proper collision
detection signal in the event of a collision.
• The Ethernet device should be connected as close as possible to the
terminator on the far end of the 75 or 93 ohm coaxial cable
segment. This will ensure that impedance mismatches due to
reflection can be predicted.
• The BNC ports of the THN-MIM7593 are connected to earth
ground. This eliminates the need for grounding the segment
connected to the module.
• Impedance mismatches may occur, resulting in signal degradation,
due to the 75 or 93 ohm coaxial cable segment being connected to a
50 ohm terminator. This may result in:
a. Increased jitter on the segment, ranging from +/-3 to +/-6 ns,
depending on the mismatch
b. Under certain conditions false collisions may be created.