Implementing a safety lockout through ladder logic
Something like this should work, it is just a simple seal-in circuit, which can only supply logic power if SW1 is closed with SW2 Open.  Then one contact on the relay closes around the enable contact of SW2, sealing it in.  Releasing SW1 will release the seal in for the relay.

Note: Both SW1 and SW2 are shown in their normal 'Non-Active' state, and SW1 is assumed to be maintained.  SW2 can be maintained or momentary as needed.







simulate this circuit &ndash; Schematic created using CircuitLab