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The XC12 connects to the Atari or the free socket of the last SIO device. Its captive cable carries data and +5 V power. With no additional socket, it must end the device chain.
MOTOR CONTROL lets the computer start and stop the motor. PLAY prepares reading; the tape moves when commanded by the Atari.
Counter and SAVE indicator
SAVE indicates recording, not simply that the recorder is powered. The counter shows tape position and helps locate recordings.
A standard XC12 uses Atari's standard cassette format. Boot tapes and BASIC programs use the same recorder but start differently.
1200XL and turbo modifications
The XC12 manual lists XE, 800XL, 600XL, 800 and 400. It does not cover the 1200XL; check SIO power before connecting to that model.
Many recorders received turbo systems or additional motor control. A case switch may belong to one of these modifications and is insufficient to identify a recording format. A turbo system requires a compatible loader.