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Theory of
Operation
Engineering
The figure below illustrates the XBN's general components and their
functions.
Field input
is routed either through an IUN function module or directly
into the base frame, depending on the XBN's slot position.
IUN FM
Signal
or
1
Thirty-two identical binary input circuits
contact, DC voltage, AC voltage, or frequencies of 10 Hz or less)
changing from logical status 0 (voltage absent, contact open) to 1 (voltage
present, contact closed) under these conditions:
Table 3: Input Signals
Sensed Input
Contact
VDC
VAC
Frequency
The user sets a switch for each input
input senses: voltage or contact.
If the V/C switch is incorrectly set to voltage, no contact changes-of-
state can be sensed by the circuit.
If the V/C switch is incorrectly set to contact, voltage differentials
greater than -12 (e.g., -10) produce a logical 1; voltages less than -12
XBN
Address
3
V/C
Debounce
Input
2
Filter Software
Circuit
Microprocessor
N2
Circuit
Figure 3: XBN Block Diagram
monitor input signals (dry
Logical 0
> 800K ohms
< 3 VDC
< 2 VAC
to select which type of signal the
Point Multiplex Modules—Multiplex Binary
4
5
EOL
6
LEDs
N2 LEDs
8
Logical 1
< 100K ohms
> 8 VDC to limit of 120
> 18 VAC to limit of 120
< 10 Hz
12 mS < Pos. Pulse < 52 mS at 10 Hz
Debounce count set to 2
Point defined as accumulator
7
7
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