Is there a CE mark requirement for positive control logic?

Question

I am looking into any requirements to obtain a CE mark that require control logic to be positive. In other words, if an electronic circuit has logic that either resets or turns the circuit off, is there a requirement that the control line activates the reset/shutdown by a low (ground) to high (such as TTL) transition or state change?

Answer 1

I don't know for sure, but I doubt that would be the case because all of the E-Stop circuits I have worked with signal shutdown on the transition from high to low; this ensures shutdown even if the E-Stop wiring gets disconnected.

Also, how would any operator ON-OFF switches work? Would they be "hot" the entire time the equipment was powered off, such that the high-low transition or low state signaled power-on, just so the high state or low-high transition could signal power-off?

Answer 2

There is no legal requirement to follow any specified design method or standard. From https://www.gov.uk/guidance/ce-marking:

It is up to you to ensure that your product complies with the essential requirements of the relevant EU legislation. The use of harmonised standards remains voluntary. You may decide to choose other ways to fulfil these essential requirements. If you don’t follow the safety requirements of a standard as it is written you will need to show that your product is as safe, by presenting the relevant documentation.