Yeah a red light would flash over the booth and the door would shut closed, hence having to put your foot in there. Alot of people buying and using these cards were like 'bullshit!' but this guy who told me about this figured to err on the side of caution anyways and ended up having to comically escape the situation with all these people looking at him.
This was like 5 years before my own time in Japan but pretty hilarious nonetheless
