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Introduction
890USE17700 April 2004 13
Integrated Power
Supply
The NIM’s built-in 24-to-5 VDC power supply provides logic power to the I/O
modules on the primary segment of the island bus. The power supply requires a
24 VDC external power source. It converts the 24 VDC to 5 V of logic power,
providing 1.2 A of current to the island. Individual STB I/O modules in an island
segment generally draw a current load of between 50 and 90 mA. (Consult the
Advantys STB Hardware Components Reference Guide [890 USE 172] for a
particular module’s specifications.) If the current drawn by the I/O modules totals
more than 1.2 A, additional STB power supplies need to be installed to support the
load.
The NIM delivers the logic power signal to the primary segment only. Special
STB XBE 1200 beginning-of-segment (BOS) modules, located in the first slot of
each extension segment, have their own built-in power supplies, which will provide
logic power to the STB I/O modules in the extension segments. Each BOS module
that you install requires 24 VDC from an external power supply.