Yamaha YIT-W12 Owner's Manual page 15

No sound is coming from the Yamaha product when playing back
music stored on a PC.
The group ID is assigned to the A1–A3
set or B1–B3 set.
Ring tone for iPhone is output from the Yamaha product.
Your iPhone received a call while it is
connected to the transmitter.
The communication between Wi-Fi devices becomes unstable.
There are signal interferences between
the transmitter and your Wi-Fi devices.
Change the group ID of the Yamaha product
and transmitter to the C1–C3 set (p.7).
As necessary, disable the ringtone output
on your iPhone.
Move the transmitter away from your Wi-Fi
devices. If the problem happens frequently,
disconnect the iPod (or the USB cable
connected to the PC) from the transmitter
and reconnect it after a while.
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