yekke2: thanks for your honest answer. This is why you can never rely upon so-called oral decisions. It could have been done in so many different ways and therefore it is important to know the actual parameters.
Note that YOU added the words “and it is assur” which is not what happened with the Rov you mentioned. His quote (as per your own admission) is that R”Shlomo Zalman said that “a sensor is switch”. OK. But then, there are many things that can happen and will engender different piskei halocho.