Intelligent Junction Box for FOUNDATION fieldbus, PROFIBUS-PA

The JB400 offers spur protection against short circuits (between + and – terminals), limiting the short circuit current in each spur. During a short circuit situation there is no effect in the other spur or the main trunk. There is a LED to indicate short circuits and JB400 has an integrated bus terminator in the models F and P.
In normal operation, each short circuit protector consumes less than 3 mA. After removing the short circuit, the spur goes back to normal operation, the protection circuit is disabled and the LED is dimmed.

Main Characteristics

  • Intelligent Junction Box for fieldbus installations in compliance with the IEC61158-2 standard (PROFIBUS PA and FOUNDATION fieldbus);
  • 4, 6 or 8 spurs;
  • Intelligent protection against short circuit in each spur, preventing the short circuit propagation. After removing the short circuit, the spur goes back to normal operation;
  • Quick and easy installation;
  • Maintenance during operation.


To better serve your application, the intelligent junction box JB400 is available in the following models:
F – For FOUNDATION™ fieldbus networks
P – For PROFIBUS PA networks
See separately their technical characteristics.


Physical layer

In compliance with IEC 61158-2

Power supply

Bus-powered 9 to 32 Vdc

Communication protocols

Profibus-PA and FOUNDATION fieldbus

Maximum trunk current

2.5 A

Quiescent current per spur in normal operation

< 1 mA

Maximum current per spur during a short circuit

50 mA

Maximum voltage drop per spur


Number of spurs

4, 6 or 8

Spur connections

Removable 3-pin terminal blocks, 2.5 mm²

Surge protector at input

Cut in 62 V, 1500 W

Cover closing

4 screws with O-ring

Housing Material



Via screws (for panel) or support with pipe clamp

Protection degree

IP 66


100 Ω resistor and 1µF capacitor selectable by switch

Status LED

On (red): spur in short circuit condition;
Off: spur in normal operation



Operation Temperature

-20°C to 70°C


-40°C to 85°C


0-95% non-condensing



Dimensions (mm)

180 x 180 x 100


1,6 kg



Download Area