Most Diverse and Flexible Line of Coded Magnetic Safety Interlock Switches and Controllers. Combine door switch monitoring and E-stop monitoring by using the CM-S41 controller. Monitor is single switch to CAT4 with the CM-S30 controller. Monitor multiple switches to CAT3 using CM-S4 or CM-S30 controllers. Monitoring multiple switches on individual channels can be achieved by using the CM-S21 or CM-S41 controllers. Easily expand your system by using the CM-SE expansion module.. All CM switches are rated IP67. Stainless steel switches are available for harsh environments.