From Pepperl+Fuchs
ACTUATOR SENSOR Interface (AS-Interface) is a simple to install two-wire network for discrete I/O, intelligent sensors, analog and safety data, encoders, light curtains and e-stops.
Specifically designed for simplicity and reliability, AS-Interface has extremely fast mounting, start-up and update times, and replaces traditional wiring architectures. It has a totally open topology—there are no limitations on how to route or split network runs. A single unshielded cable with no termination and a very high degree of noise immunity carries both data and power. In addition, AS-Interface is truly an open system, supported by all major PLC manufacturers.