Canon SPEEDLITE EL-1 Advanced User's Manual page 125

2.
Set the receiver unit.
Set the EL-1 to be controlled wirelessly from the sender as the receiver
unit ( ).
You can also use other EX-series Speedlites that are equipped with a
radio transmission wireless receiver function.
3.
Check the channel and ID.
If the transmission channels and wireless radio IDs of the sender unit
and receiver unit are different, set them to the same settings (
4.
Position the camera and flash.
Position them within the range shown at
Range".
5.
Use the joystick on the sender to select <
"Positioning and Operation
125
).
>.