An interface is defined as a place at which independent system must meets and act on or communicate with each other. In an automated system, there are devices like proximity sensors, pneumatic valves, Programmable Logic Controller (PLCs) and Computer Numerical Control (CNC) machine must be interfaced so that communication between system possible.

The systems are grouped into three interfaces categories:

1) Devices supplying data such as sensors and switches

2) Devices receiving data such as pneumatic valves, motor starts and others type of actuator.

3) Smart devices such as computer that exchange data with the enterprise data interface.

The sensors of supplying data falls into two categories: Simple sensor and Complex sensor interface.

Simple sensor interface, is basically are that has its signal begin with peripheral hardware. Peripheral hardware is a equipment used in conjunction with an industrial robot in the design of a work cell. Communication with the robot must be discrete signal only (on or off).

In this simple sensor its does not include of peripheral devices such as disk drives, printers or equipment using higher frequency binary code signals with a data format. Equipment in this simple sensor include of all types of discrete sensors, such as limit switches, proximity sensors and photoelectric sensors.

All this discrete sensors is to control the cell that would be the signal from machine tools, welders, cell controller and robot originate to operate the peripheral.

Complex sensor interface, is used with sensor that requires some signal conditioning before the data are transferred to the PLC. A complex sensor is defined as pre-processor to perform analog to digital conversion before they transferred to a higher level controller.

The complex sensor system gathering the data frequently must perform computational operations on the data to do the following:

1) Convert from analog value to digital values that are compatible with the higher level controller.

2) Detect feature or recognise patterns present in the information.

3) Compared measure data with values previously stored in sensor interface.

4) Perform coordinate transformation.

The basic requirements of complex sensor interface:

1) Computation

2) Operate at high speed

3) Bidirectional data communication

The system may require one sensor per interface if processing speed is important, it may permit one interface to handle many sensors. At present vision and force system require the most complex interface. One of the interface module the vision requires a minicomputer with memory for storage of data and vision programs.