Enabling Switch
Schmersal ZSD

Together with other safety measures, enabling switches are used to protect persons from potentially hazardous situations where machine guards need to be inactivated completely or in part in special operating modes

SCHMERSAL specializes in the design and manufacture of industrial switches, machine safety products, position sensors and related control accessories.

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If a machine is running in a special operation mode an entire or partial bypass of the protective devices might be required. In such conditions manually operated enabling switches – possibly together with other safety measures – serve to protect the operator from hazardous situations.

Although safeguards are designed to provide appropriate protection in all operating modes, exceptions are admissible if it is otherwise not possible to operate a machine practically. These exceptions will typically include the setting up of a machine, service work or observing operating processes, so-called process observation.

In these cases additional actions must be taken to guarantee personal protection of individuals even in special operating modes. Enabling switches are frequently used in such situations.

They serve to permit commands (for example for hazardous movements) from other control stations. Start signals for hazardous movements must not be triggered by an enabling switch alone.

If the operator releases the pushbutton, or in the case of the 3-position version, the operator overpresses the trigger point of the pushbutton then the “Go” signal is interrupted by a forced open NC contact.