Siemens profibus master cm 1243 5 profibus slave cm 1242 5 siemens 6gk7243 5dx30 0xe0 the siemens 6gk7243 5dx30 0xe0 cm 1243 5 is a profibus master din rail communication module it allows the connection of programming devices and operator panels with a profibus interface the modules are intended for use in factory automation particularly for mechanical engineeringwith the cm 1243 5 low cost distributed automation solutions can be implemented in simple cases or even complete plant auto