Siemens SM322 Digital output, isolated, 16DO, 20-pole, 4A16 Digital output modules permit the output of digital signals from the PLC to the process by converting the internal signal level of the S7 300 into the external signal level required by the process. They are suitable for connecting solenoid valves, contactors, small power motors, lamps and motor starters, for example. By design the digital output modules feature the following mechanical characteristics are compact design, easy to install and User