Do you know the difference between NTSC and PAL Atari games? From the 2600 FAQ and console compatability FAQ:
NTSC (National Television Standards Committee), PAL (Phase Alternating Lines) and SECAM (SEquentiel Couleur Avec Memoire) are different worldwide, generally incompatible television standards. Some short, not completely accurate information follows.
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NTSC US/Japan 60hz/30/525
PAL Europe 50hz/25/625
SECAM France & many others 50hz/25/625
So how does this affect Atari games?
Each cartridge tells the 2600 when to generate TV line sync pulses. This means that using an NTSC cartridge in a PAL console, or vice versa, will cause synch pulses to be generated at the wrong frequency. The net effect of this is that some TVs will "roll" the picture, and may need the vertical hold control to be adjusted. Some TVs will handle the incorrect synch frequency transparently though.