Contemporary Control Systems AI Active Hubs - Manual (Page 5)

TD675100-0M
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Introduction
1.1 Description
The ARCNET Interconnect (AI) series of external fixed port
hubs provide a low cost method of expanding ARCNET local
area networks. Expansion methods include the use of repeaters,
links and hubs. Repeaters are used to extend a wiring segment
using the same cabling technology. A link allows the mixing of
two cabling technologies within one segment. A hub allows for
the addition of a segment and support for distributed star
topologies. The AI can implement all three expansion methods
depending upon the number of ports on the AI. The AI2
provides two ports for repeater and link applications while the
AI3 implements the hub function. However, the AI2 and AI3
utilize the same robust hub timing electronics found in
Contemporary Controls’ (CC’s) MOD HUB series of modular
active hubs. This includes precision delay line timing, digitally
controlled timers for dependable operation and reduced bit jitter.
The AI operates from either low voltage AC or DC power. For
DC operation, a voltage source in the range of 10 to 36 volts is
required. For AC operation, a voltage source in the range of 8 to
24 volts is required. Companion regulatory approved
transformers are available under separate model numbers for
UL and CE Mark applications.
The timing electronics 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. The AI series supports variable data rates
from 78 kbps to 10 Mbps in order to accommodate newer
ARCNET controller chips and popular EIA-485 transceivers.