Canon Speedlite EL-5 Advanced User's Manual page 101

5.
Set the wireless radio ID.
Press the joystick horizontally or turn < > to select the position (digit)
to set, then push the joystick straight in.
Press the joystick vertically or turn < > to select a number in the
range 0–9, then push the joystick straight in.
Set a 4-digit number the same way, then select < >.
The < > lamp is lit in green when communication is established
between the sender and receiver.
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