Introduction: Industrial network nodes in harsh environments
In harsh environments such as open-pit mines, tunnel engineering, rail transit vehicles, and ship decks, ordinary industrial switches often fail frequently due to insufficient protection levels (dust, splashing water, condensation). The Hirschmann OCTOPUS OS20/OS24 series managed switches are designed specifically for this type of scenario, featuring a fully sealed metal housing and an overall protection level of IP65/67. They are equipped with M12 circular connectors (D-code) and 7/8 "power interfaces, which can withstand high-pressure water flushing, salt spray, and condensation environments. The series offers 9 100Mbps M12 ports (ports 2-9 of the OS24 model support PoE+and comply with IEEE 802.3at), supporting redundant power supplies (24-48V or 72-110V wide voltage), with operating temperatures covering -40 ° C~+70 ° C, and certified for railways (EN 50155), ships (GL), and vehicles (e1). This article is based on the official installation manual and systematically reviews the model decoding, M12 power and signal contact wiring, waterproof installation, EMC ferrite configuration, and PoE management of OCTOPUS OS20/OS24, providing detailed guidance for engineers on network deployment in harsh environments.
Chapter 1 Product Positioning and Model Decoding
1.1 Unique positioning of OCTOPUS family
The OCTOPUS series complements the Hirschmann Open Rail (RS series) and MICE series: Open Rail is suitable for standard industrial cabinets, MICE is suitable for 19 inch racks, and OCTOPUS is designed for IP65/67 protection requirements scenarios such as outdoor cabinets, train carriage bottoms, port cranes, etc. The difference between OS20 and OS24 lies in their PoE capability: OS20 is a pure data switch (9 100Mbps ports, no PoE), while OS24 provides 8 PoE+ports (ports 2-9) and 1 non PoE port (port 1), with a total PoE power budget of 61.6W.
1.2 Model Code Analysis (Manual Table 2)
Meaning of key positions:
Position 6-7: Number of special ports (000 or 088, where 088 represents 8 PoE+ports)
Position 8-9: Number of 100Mbps ports (099, fixed at 9 100Mbps ports)
Position 12-13: Upstream port type (T5, i.e. M12 D-code twisted pair port)
Position 16: Temperature Range (T=-40 ° C~+70 ° C)
Position 17: Power Characteristics (A=24-48V DC, M12 5-pin); F = 24~48V DC, 7/8 "5-pin; N=72~110V DC, 7/8" 4-pin)
Position 18: Certification (E=UL+along the railway/train; F=UL+railway+GL vessel+e1 vehicle mounted)
Existing models (manual table 2):
OS20-000900T5T5TAFBHH (24V, M12 power supply)
OS20-000900T5T5TNEBHH (110V, 7/8 "power supply)
OS24-080900T5T5TFFBHH (24V, 7/8 "power supply, PoE)
OS24-080900T5T5TNEBHH (110V, 7/8 "power supply, PoE)
Chapter 2 Connection of Power Supply and Signal Contact Points
2.1 Detailed Explanation of Three Power Supply Characteristics
OCTOPUS is divided into three characteristics based on power interface type and voltage level: A, F, and N
Feature A (24-48V DC, M12 5-pin connector):
Input voltage: 9.6~60V DC (rated 24~48V)
Interface: 5-pin M12 A-code (with ELWIKA 5012 PG7 connector included)
The signal contacts are integrated into the same connector (pins 2 and 5 are FAULT)
Buffer time:>10ms
External fuse: 2A slow melting
Feature F (24~48V DC, 7/8 "5-pin connector):
Input voltage: 16.8-60V DC (rated 24-48V)
Interface: 5-pin 7/8 "connector (power specific, pin allocation as shown in Table 8)
Signal contact: Independent 5-pin M12 connector (to be purchased separately)
Need to install ferrite magnetic rings (included) to meet EMC requirements
External fuse: 7A slow melting
Characteristic N (72~110V DC, 7/8 "4-pin connector):
Input voltage: 50.4~138V DC (rated 72~110V)
Interface: 4-pin 7/8 "connector (power specific)
Signal contact: Independent 5-pin M12 connector (to be purchased separately)
External fuse: 2.5A slow melting
2.2 Railway Standard Special Warning (EN 50155)
Critical safety warning: According to EN 50155 clause 5.1.1.1, the nominal voltage of 48V supplied by the train may temporarily exceed the SELV threshold of 60V. Additional measures must be taken to limit the surge voltage to below 60V, or to use a lower nominal voltage. This directly affects on-site wiring and fuse selection.
2.3 Signal Contact (FAULT) Wiring
Feature A: The signal contacts are integrated into a 5-pin M12 power connector (pins 2 and 5)
Feature F/N: The signal contacts need to be wired through independent 5-pin M12 A-code connectors (such as ELWIKA 5012 PG7), with pin assignments shown in Table 6 (pins 2 and 5 are FAULT, others are not used)
Contact electrical parameters: maximum 1A resistive load, maximum 48V DC, SELV.
2.4 Key requirements for waterproof sealing
When using the ELWIKA 5012 PG7 connector, the cable diameter must be between 4mm and 6mm, exceeding this range will damage the IP65/67 sealing. All unused M12 ports and power sockets must be sealed with protective plugs (Attachment 942 057-001/002).

Chapter 3 Mechanical Installation and Grounding
3.1 Installation method and heat dissipation requirements