Canon SPEEDLITE EL-1 Advanced User's Manual page 174

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 an
optical transmission wireless receiver function.
You can use any of A, B, or C as the firing group (1).
3.
Check the channel.
If the communication channels of the sender and receiver units are
different, set them to the same channel (
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
174
).
>.