Canon Rebel T2i Quick Start Manual page 113

Phantom Power must be enabled
All audio devices that accept an input will have
a "+48 V" button. This can be turned on to
deliver "phantom power" to a condenser
microphone. It should never be turned on when
a dynamic microphone, like the SM58, is
plugged into the channel.
To use the AVX wireless condenser microphone
through the receiver, go into the Menu system
to enable the Phantom Power for the input
channel. Here I am recording on channel one.
Phantom Power is
indicated by the +48V
note underneath the
channel and the lightning
bolt symbol.