Canon SPEEDLITE EL-1 Advanced User's Manual page 115

5.
Set the wireless radio ID.
Push the joystick to the left or right or turn < > to select the position
(digit) to set, then push the joystick vertically.
Push the joystick up or down or turn < > to select a number from 0
to 9, then push the joystick vertically.
Set a 4-digit number with the same procedure and select < >.
When transmission between the sender unit and receiver unit is
established, the < > lamp is lit in green.
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