Building automation with ASi

AS-Interface – building automation

The advantages of AS-Interface – such as simple, cost-saving installation and high degree of flexibility – have now become familiar in Building Automation as well. Numerous companies are relying on the ASi installation system for applications such as controlling fire and smoke damper systems, shutter drives or heating and cooling ceilings using analog output modules. Damper actuators with flow regulators can also be connected to the controller through the MP-Bus Gateway. It is also possible to process EnOcean signals from wireless buttons and sensors through ASi. Customer proximity is our hallmark, which means we stand by you in word and deed and are open to custom-tailored solutions. Just contact us.

Safe smoke extraction

Our solution for smoke extraction and fire damper control is suitable for many system sizes (according to VDMA 24200-1) and offers you safety up to SIL3 PLE. It provides 1922 safe inputs and outputs per group and up to 31 groups in total.


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Lighting and HVAC control

Take advantage of the minimal cabling complexity and cross-trade integration when controlling your lighting and HVAC with Bihl+Wiedemann. Our solution can be brought into operation quickly and is flexibly expandable.


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Ventilation technology

In the ventilation technology sector (heating control and CO2 automation), we offer one system for multiple trades. EnOcean and an MP-Bus are integrated, while both analog and digital inputs/outputs are available. Quick and easy commissioning are yet another advantage.


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Basic concept of AS-Interface 

AS-Interface is an industrial networking solution for automation systems. It is designed for connecting simple field I/O devices such as binary ON/OFF, analog and safety I/O devices according to EN 50295, IEC 62023-2. Using only a two conductor flat or round cable (ASi cable, 2 x 1.5 mm2, 16 AWG) to connect all nodes to the master using a free topology. This is the main advantage of this system compared to conventional, parallel wiring, where every single signal has to be wired directly to the control system.

Data and power are available in the same ASi cable. Every node or module has its own address for accessing its data. The nodes can be addressed from 1 to 31 (single address, or, with extended addressing, there are 62 addresses available (1A to 31A and 1B to 31B). Single addresses and modules with extended addressing (AB modules) can share the same network.

The structure

The ASi Master/Gateway controls the ASi network and acts as a direct link to the host (PLC, Building Management Systems, etc.). Combined with an integrated mini-PLC functionality the master can also be used for pre-processing or as a stand-alone device without the need for a host controller (programming language IL or C).

A Gateway is an ASi Master, and simultaneously a node to higher level network (PROFIBUS, EtherNet/IP, Modbus, etc.). AS-Interface is the lowest level of the automation pyramid intended for Actuator/Sensor networking.


Free topology

ASi supports free topology such as Star, Ring, Linear and Mesh network (see examples below).

Ring topology

ASi network

The simple and highly flexible ASi network bus is one of the great strengths of the system. The polling  principle allows the use of any topology and features a variety of different field and control cabinet modules. Whatever the requirements in your building we make it possible to record both digital and analog values and control either type of actuator. Whether a ventilation flap with four digital and four analog outputs, an analog output module for controlling heating/cooling ceilings, or special equipment such as an MP-Bus or EnOcean gateways.

You can also process both ASi standard and ASi Safety (up to SIL3) data over the same ASi network. The data can be processed in the master or passed on to the higher level building management system through the fieldbus interface on the master.

ASi features per line

Medium Unshielded two conductor flat cable *
Signal Power Supply and data in one cable with max. 8 A
Number of Nodes per ASi line up to 62
Number of I/O Binary up to 248 Inputs and 248 Outputs
Number of I/O Analog up to 124 Inputs or Outputs
Cycle Time 5 ms
Transmission Rate 167 kbit/second
Error Protection Identification and repetition of faulty frames
Supported Topology Star, Ring and Linear
Safety Up to SIL 3, Category 4, PLe (EN 62061, EN 61508, EN ISO 13849-1, EN 954-1)
Cable Length 100 m (extensible up to 1000 m)

* Of course other cables, such as NYM-J or E90 cable, can also be used.


Gateways for linking to any building management system

Optionally with integrated controller (mini-PLC) also usable as stand-alone devices

  • Permanent line path monitoring
  • Plain text messages on the display and to the BMS
  • Pre-parameterized on request

Power Supplies

  • Single phase
  • 3 phases
  • 24 V to ASi
  • 1,8 A, 2 A, 4 A, 8 A
  • Decoupling unit for 2 ASi networks

    Module for controlling damper actuators

    • For ventilation, fire and smoke dampers
    • Inputs for end position detection
    • Additional input e.g. for fire alarms
    • Output for controlling dampers
    • Supply of the drives from ASi or external 24 V

    Module for increased safety requirements

    • For ventilation, fire and smoke dampers according to Swiss standard for soldered strut and fire alarms
    • Inputs for end position detection
    • Control up to SIL 3/Cat. 4/PLe
    • Supply of the drives from ASi or external 24 V

    Module for controlling shutter drives

    • 2 shutter drives (230 V AC) per module controllable
    • 4 inputs for switches
    • For 4-/5-conductor-shutters
    • Trip-/position recognition

    Relay Module for field applications (230V/24V)

    MP-Bus Gateway

    EnOcean ASi wireless module

    • Version with 2 relays and 4 inputs for e.g. damper actuators etc.
    • Version with 4 relays and 4 inputs for e.g. light, blower and fancoil control
    • Linking MP-Bus participants (e.g. flow regulators) to ASi
    • Integrated 230 V / 24 V power supply
    • For linking EnOcean wireless modules (e.g. pushbuttons, temperature sensors, window contacts, presence detectors) to ASi
    • Available in individual designs

    ASi Safety


    Gateways with integrated Safety controller

    • ASi Safety Module to control Fire/Smoke Damper Actuators (up to SIL 2)
    • Mixed Input / Output Modules
    • For floating contacts, OSSD outputs and safety mats
    • Electronic outputs
    • Relay outputs
    • Speed/Standstill monitoring

    Digital and analog input and output modules

    In stainless steel, IP20

    For example:

    • Digital 4I/4O
    • Digital 8I
    • Digital 8O
    • Relay outputs (230 V AC)

    In surface-mounted box, IP54

    For example:

    • 2 analog (0-10 V) + 2 digital outputs for heating/cooling ceilings
    • Digital 4I/4O
    • Input Modules for CO2, relative humidity, etc.

    Coated module for flush-mounted boxes

    • 4 digital inputs for standard switches




    Cabinet modules

    • 4E/4A, 8E/8A
    • 0/4...20 mA
    • 0...10 V
    • Pt100, Pt1000
    • Thermocouples
    • Digitale I/O Modules
    • Pt100, Pt1000
    • Analog  I/O Modules



    Diagnostics/circuit extension

    Advantages at a glance


    • Save hardware by reducing I/O cards, cabinets and wiring
    • Robust, globally standardized industrial bus with already more than 27 million installed nodes
    • Simple electronics with robust performance in industrial quality
    • Free choice of network topology
    • Quick installation, reduce maintenance and shorten testing time,fast commisioning and ability to expand the system
    • Easy commissioning, and opportunity to expand the system
    • Transmission in real-time
    • Avoid wiring errors (no risk of faulty electrical connection)
    • High resistance against EMC noise
    • Fast error localization, spontaneous diagnostics and enhanced diagnostic options


    ASi is fully backwards compatible. This means that a master according to the last specification 3.0 can communicate with all existing nodes according to the different specifications 2.0, 2.11 and 3.0. This guarantees a future proof investment.

    Simply to connect

    Owing to the yellow profile cable* and the piercing technology, ASi modules are easily expandable and can be connected reverse polarity protected.


    * Of course other cables, such as NYM-J or E90 cable, can also be used.

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    Control of fire dampers and smoke extraction dampers

    Find out how you can reduce fire loads in the building by up to a factor of 30 with ASi. Thanks to the ASi profile cable, fire dampers and smoke dampers can be supplied with data and energy via a single two-wire cable.


    The standardized fieldbus system AS-Interface (ASi) helps you drastically reduce your wiring complexity. You also benefit from free choice of topology and cost-effective integration of safety features on the same infrastructure.

    Products for building automation available in the webshop

    ASi advantages, such as freedom of topology, extremely simple installation or high flexibility, have also become widely adopted in building services engineering. Here you will find our wide range of products.

    Do you have questions about our products and solutions?

    ASi – A resource-saving technology

    Thanks to the greatly reduced wiring effort with AS-Interface, you save assembly and material costs. This saves valuable resources.


    More information!