Appendices
A - 42
NX-series Digital I/O Unit User’s Manual (W521)
Unit name
Transistor Output Unit
Model
NX-OD2258
Number of points
2 points
External connection 
terminals
Screwless clamping terminal block (8 ter-
minals)
I/O refreshing method
Output refreshing with specified time stamp
Indicators
TS indicator, output indicator
Internal I/O common
PNP
Rated voltage
24 VDC
Operating load voltage 
range
15 to 28.8 VDC
Maximum value of load 
current
0.5 A/point, 1 A/Unit
Maximum inrush cur-
rent
4.0 A/point, 10 ms max.
Leakage current
0.1 mA max.
Residual voltage
1.5 V max.
ON/OFF response time
300 ns max./300 ns max.
Dimensions
12 (W) x 100 (H) x 71 (D)
Isolation method
Digital isolator isolation
Insulation resistance
20 MΩ min. between isolated circuits (at 
100 VDC)
Dielectric strength
510 VAC between isolated circuits for 1 
minute at a leakage current of 5 mA max.
I/O power supply 
method
Supply from the NX bus
Current capacity of I/O 
power supply terminal
IOV: 0.5 A/terminal max., IOG: 0.5 A/termi-
nal max.
NX Unit power con-
sumption
• Connected to a CPU Unit
0.85 W max.
• Connected to a Communications Cou-
pler Unit
0.50 W max.
Current consumption 
from I/O power supply
40 mA max.
Weight
70 g max.
Circuit layout
Installation orienta-
tion and restrictions
Installation orientation:
• Connected to a CPU Unit
Possible in upright installation.
• Connected to a Communications Coupler Unit
Possible in 6 orientations.
Restrictions: No restrictions
OUT0 to OUT1
This Unit uses a push-pull output circuit.
IOV0 to 1
IOG0 to 1
Terminal block
Internal circuits
Isolation circuit
Drive circuit
NX bus 
connector 
(left)
I/O power supply +
I/O power supply −
I/O power supply +
I/O power supply −
NX bus 
connector 
(right)