Cabletron Systems THN-MIM Manual De Usuario

 

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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. 

 

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.