Well it can not only be a LED that is supposed to be one-way, but the whole circuitry driving it. Likewise for the receptor. With some appropriate review of the

Well it can not only be a LED that is supposed to be one-way, but the whole circuitry driving it. Likewise for the receptor. With some appropriate review of the physical design, you can have a reasonable expectation that the comm will be limited to one-way, with no way for arbitrary SW to modify the direction.