Zweikanalton
How It Works

mode
existing OIRT 6.5 MHz or BG 5.5 MHz sound carrier contains:
2nd OIRT 6.258 MHz or BG 5.742 MHz carrier contains:
pilot tone in 2nd carrier:
mono
mono
carrier is absent
none
stereo
mix of left & right (L+R)
right audio channel (R)
54.6875 kHz 50% AM with 117.5 Hz
bilingual
1st language
2nd language
54.6875 kHz 50% AM with 274.1 Hz

Question: What does the second carrier contain?
Answer: The second carrier contains a 54.6875 kHz pilot tone for stereo or bilingual.