Siemens din rail compact ethernet switch module csm 1277 siemens 6gk7277 1aa10 0aa0 p the 6gk7277 1aa10 0aa0 is a csm 1277 24v din rail ethernet switch module of compact design for use in the simatic s7 1200 the csm 1277 can be used to multiply the ethernet interface of the simatic s7 1200 for simultaneous communication with operator panels programming devices other controllers or the office world p p the csm 1277 and the simatic s7 1200 controller can be used to implement simple auto