[time-nuts] Form factor

Hal Murray hmurray at megapathdsl.net
Tue Jan 4 20:29:45 UTC 2011

[From a couple of weeks ago...]

>>Opto-isolater?   Why not just use fiber cable between cards.

> I have only ever seen point-to-point versions, I needed 7 cards connected.

You can make a multi-drop setup with 2n unidirectional optical links.  The 
trick is to send all the links to a common node and OR the signal together 

Consider the old coax Ethernet...   The coax was an OR gate.

There were rules about the length (timing) of the long coax and the short 
drop cables between the host and the transceiver.  You can use longer drop 
cables and still meet the rules if you use a shorter coax.  Push that all the 
way and you get close to the typical setup that used twisted pair phone 
wiring to a hub (not switch).

The early transceivers used 3 signal pairs, one for collision, but you can 
encode that on the data link.

You can replace the copper link in that setup with fiber.

One disadvantage of this approach is that the hub needs power.

These are my opinions, not necessarily my employer's.  I hate spam.

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