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Terminology and Product Concepts

The Ethernet advanced physical layer (APL) defines switched architecture. Cross talk between instruments is impossible, which enhances communication stability and has a long-lasting positive effect on availability. Learn more about the Ethernet-APL infrastructure on this page.

  • Segment is the name for each connection between switches or between switches and instruments.
  • Trunk is the long-reach cable between switches. It has high power and signal strength and can be up to 1000 m long.
  • Spur is the connection cable for an instrument. It can be up to 200 m and has lower power and signal strength. Spurs can be selected as intrinsically safe.

Product Concepts

Ethernet-APL Power Switch

The Ethernet-APL power switch connects the Ethernet-APL network to the facility Ethernet or backbone. It also provides power to the trunk line. This power switch is typically installed in the cabinet inside the control room and is externally powered.


  • APL trunk power and communication
  • Supports ring redundancy on the facility Ethernet
  • Cabinet installation in Zone 2 / Div. 2
  • Externally powered

Ethernet-APL Field Switch

Field switches provide power to the spur line where the instrument is connected. The spur has lower requirements for signal strength and power. Two types of field switches enable any kind of topology—the Ethernet-APL field switch and the Ethernet-APL DIN-rail switch.

The Ethernet-APL field switch for Zone 1 / Div. 2 installation receives power from the trunk. It connects APL spurs to the trunk. Outputs are intrinsically safe, supporting connections into Zone 0 / Div. 1.


  • Outputs intrinsically safe up to Ex ia IIC
  • Instruments in Zone 0 / Div. 1
  • Field installation in Zone 1 / Div. 2
  • Trunk powered

Ethernet-APL DIN-Rail Switch

The Ethernet-APL DIN-rail switch is a field switch for installation in a control cabinet or junction box. It connects Ethernet-APL spurs to the plant’s Ethernet backbone. It draws power for itself and the spurs from external auxiliary power.


  • Ethernet-APL spur power and communication
  • Supports ring redundancy on the facility Ethernet
  • Cabinet installation in Zone 2 / Div. 2
  • Externally powered
  • Intrinsic safety at the spur: Ex ic IIC or Ex ia IIC


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