Axis 2n SingleTalk User Manual page 40

Accident Hazard
Make sure that the button is safe, i.e. that the minimum isolation distance
is 1.5 mm and the minimum breakdown voltage value is 1,500 V. The
button contacts may not be connected to any other circuits. If any of the
above conditions cannot be met, use voltage control.
You can use an N/O or N/C button or both.
Refer to the rear cover for internally connected terminals.
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