@oeconomicus

Which is exactly the current solution: Users toggling in a code using the only input available?

But that "code" (even if interpreted as Morse as @Etienne did) is stupidly based on extended delays. From a human factors standpoint, there's just no good reason for that solution. The underlying problem is essentially: how can a user "escape" a normal input channel in a way that is unlikely to be triggered in normal operation or accidentally (such as by a child screwing around). There are countless ways to do that in a manner that doesn't involve multi-second pauses. Even for a device that would be inherently limited by a 0.5 baud rate, you're looking at 60% signal loss/inefficiency here. Even with simple counter-based sequences you could probably get people to do this not only 8 times faster, but give them the experience that they did something more than spend most of their time waiting around watching the seconds tick by. 4269864b5939697ca80615acf6a69bf5cf0dcc513895197ff65f41e99d245277