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AS-Interface, the Actuator Sensor Interface and its distinctive ‘yellow cable’ is one of the most innovative networking solutions in modern automation technology.

Conceived in 1990 as a cost-efficient, feature-rich alternative to conventional hard-wiring, AS-Interface has now been proven in hundreds of thousands of products and applications spanning the en – tire automation spectrum.

AS-Interface offers many of the benefits of more powerful and expensive fieldbuses, but at much lower cost and at much simpler application. The complete network is controlled automatically by a ‘master’ which polls the network sending and receiving data from each connected device in turn. It automatically senses and registers any connected devices, thus neither configuration nor applicationspecific software for the master is necessary

Unique technology

Due to the cable structure, AS-Interface offers a unique mounting technology.

Without any cutting or removal of insulation, sharp pins penetrate the cable insulation making the electrical contact as the connection elements are closed. This technology ensures protection up to IP 65.

Cost savings

In general, applications from as few as ten sensors and actuators to very large systems can benefit, especially when the whole life cost advantages are taken into account. Distributing the input and output
functionality is one starting point for cost savings, enabling point to point wiring systems to be reduced to a single cable, eliminating or reducing cable trees, service cabinets and multiple connectors. The special AS-Interface connection technology replaces labour-intensive wiring. The tree structure permits better optimised system design and improved layouts, bringing easier installation and maintenance. Network configuration is eliminated.

System Survey

• Single master-slave principle
• Up to 62 slaves with one master
• Per slave up to 4 digital inputs + 4 digital outputs
• Max. 248 digital inputs and outputs
• Additional 4 parameter bits/salve
• Also possible: analogue I/O
• Electronic addressing of slaves
• Free structure of the network
• AS-Interface® – a bus system,which subsitutes parallel wired installation from pic to sensors and actuators.• Data and energy in the same cable


• 1 Master and max. 62 slaves


• Total cycle time < 10 ms –with max. number of 32 slaves


• Master-slave principle: The master calls and theslave answers immediately

Cable power

The yellow cable can carry up to 8 A, which means that no ad d itional wiring is required in typical installations. Several hundred mA may be drawn by a single slave device on the network. Where higher ower is needed, or for emergency stop situations, a black secondary DC or AC power cable offers complementary advantages. If round cable is preferred, a wide variety of screw and push-fit termination modules offer this, with no performance com promise.

Products with AS-Interface

WERMA Signaltechnik GmbH & Co. KG has been a member of the AS – Interface® Association since 1996.

WERMA’s product range encompasses the LED/Buzzer Combination 450 with acknowledgement function for ASInterface ®. The combination unites a very bright light signal with the powerful sound of a buzzer. By gently pressing the front surface of the product the audible signal can be turned off in a matter of seconds.

This acknowledgement signal is fed back to the master via the AS-Interface Bus. In addition, the new LED Installation Beacon(Multicolour) 239 is available for AS-Interface®. This is suitable for the extended addressing (A/B engineering) of up to 62 modules. This beacon is provided with electircity via the bus. WERMA’s product range also contains products with SInterface ® for KombiSIGN 50, 70 and 71 as well as customised developments. The entire BUS electronic system is integrated in the element placed at the base of the signal tower.

 The KombiSIGN AS-interface® elements offer the customer beneficial features such as an addressing socket and status LEDs. A user-friendly sliding switch inside the module

can be used to provide the power supply required for the signal towers

from an external 24 V auxiliary voltage or via the integrated bus bypass.