Kessel SG 400 V Mono Notice D'utilisation D'origine page 54

Mono/Duo ATEX level sensor
Connect the ends of the level sensor's leads to the terminals [10].
The level sensor's connection is identical for both Mono and Duo systems.
Only connect level sensors that satisfy the ATEX requirement to the
Zener barrier.
54
Overview of connections for the level sensor
Wire colour
Note: When extending the cable of the level sensor use
KESSEL-junction box (art. No. 28799).
[10]
Installation and operating manual
Name on Zener barrier
red
black
HAZ
bl bl
3 4
(-)
(+)
rt/RD sw/BK
3 (plus)
4 (minus)
010-532_03