Canon EOS 750D Instruction Manual page 18

Basic Operation and Settings
Cable Connection Cautions
When [51: Wi-Fi/NFC] is set to [Enable], connection via interface cable,
stereo AV cable, or HDMI cable is disabled. Set [51: Wi-Fi/NFC] to
[Disable] before connecting a cable.
When the camera is connected to a computer, printer, GPS receiver, TV
set, or any other device with an interface cable, settings for [Wi-Fi/NFC]
cannot be changed. Disconnect the interface cable before changing any
settings.
Cards
If there is no card in the camera, it cannot be connected to a wireless
LAN. Additionally, the camera cannot be connected to a wireless LAN to
use the Wi-Fi functions [l], [m], or [o] unless the card has images
saved on it.
Using an Eye-Fi Card
When [51: Wi-Fi/NFC] is set to [Enable], image transfer using an Eye-Fi
card is disabled.
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