ADLINK ND-6067 - Manual (Page 16)

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1.4 EIA RS-485 Standard
The EIA RS-485 interface is a communication standard developed for
multi-dropped systems that can communicate at high rate over long distance.
The standard RS-485 can operate at speed up to 10 M bps over cable length up
to 4000 feet.
The RS-485 interface can support up to 32 drivers / receivers on the same line.
This allows actual networking applications on a parity line system (sometimes
called multi-drop).
The RS-485 uses differential transmission on a balance line. Its easy wiring
make it popular to use in industrial applications.
1.5 RS-485 on NuDAM
The NuDAM improves the RS-485 capability for minimizing the user‘s cost. On
each NuDAM module, a half-duplex RS-485 transceiver is used to communicate
with other modules. A single twisted pair of wires, which provides standard
differential transmission, is used to transmit and receive data between modules.
The high input impedance of each NuDAM receiver allows up to 128 NuDAM
modules on the same RS-485 bus without using a signal repeater.
The maximum transfer rate of NuDAM is 115.2Kbps which is lower than the
maximum speed of the RS-485 standard. The slew-rate limiter on every RS-485
transceiver of NuDAM is very useful for transmitting error-free data, minimizing
EMI, and reducing reflections caused by improperly terminated cables.
The NuDAM on a network may not use the same power supply. Therefore, the
voltage difference between ground of the modules may exist.
Excessive output current and power dissipation caused by faults or by bus
contention are prevented by the current limiter and the thermal shutdown
circuitry inside the NuDAM.