https://www.edwards-signals.com/products/control-devices/251-series-patened-non-contact-safety-interlock-guardswitch
Patened, Non-Contact Safety Interlock GuardSwitch - 251 Series | Edwards Signaling
The Patented Non-Contact Safety Interlock Switch 251 F7 GuardSwitch is designed to deliver dependable, fail-safe protection in industrial environments.
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