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JUMP tickets are the classical paper tickets with a magnetic strip. They look like this:
They have to be validated at the beginning of each journey, so each time you enter the metro or board a tram or bus. They don't have to be validated upon exit.
JUMP tickets have to be inserted into the orange machines. The "red machine with the white eye" is for the newer MOBIB tickets.
Here is an extract from the STIB's official website:
Users must validate their transport ticket prior to every journey. At above-ground stops, the transport ticket must be validated every time the user boards or connects to a bus or tram. In underground metro and pre-metro stations, users must validate their transport tickets in the inspection areas.