Contemporary Control Systems EXP Expansion Modules User Manual - Manual (Page 5)

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Introduction
1.1 Description
The MOD HUB series of modular active hubs provides a
convenient and flexible method of expanding ARCNET local
area networks. EXP expansion modules are installed into the
MOD HUB that support the particular cabling technology
desired. The MOD HUB is available with either four expansion
slots or twelve. Since most expansion modules support four
ports each, a total of 48 ports can be provided within one hub.
MOD HUBs can be cascaded via an expansion port on each hub
to expand the network to the limit of the ARCNET technology.
The MOD HUB is provided with an integral universal voltage
power supply, four or sixteen slot card cage and internal timing
module permanently installed into the hub's backplane. There
are no expansion modules provided with the MOD HUB. The
timing module uses a precision delay line timing generator
which regenerates the incoming ARCNET signal without
introducing excessive bit jitter. The regenerated signal is then
sent to all other ports on the hub. A watchdog timer is included
to prevent the possibility of hub lockup eliminating the necessity
of cycling power on a failed hub. The hub unlatch delay time is
derived from a crystal oscillator for high accuracy and
repeatability.
Active hubs increase the robustness of ARCNET networks.
They maximize the distance that can be achieved on each cable
segment
— up to 2000 feet on coaxial segments. They prevent
interference to the network by squelching reflections caused by
open or shorted cable segments attached to the hub. Unused hub
ports need not be terminated. Active hubs allow for a distributed
star topology, thereby minimizing the cabling required in a
plant.
TD401600-0M
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