GE F650 User Manual page 212

7.1 COMMUNICATIONS
Q12. May I connect URs and F650s to the same Ethernet?
A12. Yes, either in cable as in fiber, or even mix them.
Q13. How do I connect with fiber 10-BASE-FL UR relays with 100-BASE-FX F650 relays?
A13. Take into account that an UR is never connected directly to a F650 (neither two UR nor two F650 with each other)
but they are always connected through a hub or switch. The hub or switch where the URs are connected must be
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10-BASE-FL and the hub or switch for the F650 must be 100-BASE-FX.
Q14. How do I connect with cable 10_BASE-T UR relays with 10/100-BASE-TX F650 relays?
A14. The answer to this question is as described before but also in this case there is an advantage added, because the
hub 10-BASE-TX port is able to understand a 10-BASE-T port. This means that a hub 10-BASE-T port may be
connected to an UR or a F650, and a hub 10/100-BASE-TX port may be connected either to an UR or F650.
Q15. What happens with fiber optic connectors compatibility, because the hub that I have has a different
connector to the one of the F650, although both are 100-BASE-FX?
A15. Just buy fiber cables with the appropriate male connectors. For the UR and F650 side we need the same
connectors, ST type, for the hub side, the correspondent ones. And in what concerns to the fiber type, it is used the
same for 10 as for 100, it is the 50/125 or 62.5/125 multimode, this last one allows longer distances.
Q16. What is the difference between a hub and a switch?
A16. In a repeater type hub (shared hub), one unit talks and the rest listen. If all the units are talking at the same time
there may be collisions in the messages, what may produce certain communication delays.
The switch (switched hub) has very powerful processors and a lot of memory and it is much more expensive than
the hub. It directs messages to the proper destination avoiding collisions and allowing a much more efficient
communication.
Q17. Why do we have 10/100 compatibility for cable but not for fiber?
A17. The cable has some advantages that the fiber does not have, and it is that the signal attenuation in short and
medium distances, is worthless and this is truth for low and high frequency signals. By the contrary, the light in one
fiber optic is highly attenuated, being much worse in case of high frequencies than in the low ones. The 10-BASE-FL
fiber transmission is performed in a wavelength of 850nm, what allows a less expensive electronic than the 1300 nm
used in 100-BASE-FX fiber transmission. Using, in both cases, the same glass multimode fiber type, the attenuation
to 1300 nm is lower than the 850 nm ones, this way the greater attenuation of the 100 Mbits is compensated. There
is another fiber standard, the 100-BASE-SX, which uses 850 nm to 100 Mbits, being compatible with the 10-BASE-
FL one, although it sacrifices the maximum distance to 300 m. Nowadays, this standard has not had success among
Ethernet equipment manufacturers and suppliers.
7-2 F650 Digital Bay Controller
7 FREQUENTLY ASKED QUESTIONS
GEK-113000AE