Canon SPEEDLITE EL-1 Advanced User's Manual page 155

Before performing the operations below, attach a Speedlite or transmitter to all the cameras
to be used for linked shooting. For details on setting other devices, refer to the Instruction
Manual of the devices.
1.
Select <
2.
Set to normal shooting mode.
> with the joystick.
Press the joystick up, down, left, or right, or turn <
< >, then press the joystick vertically.
Display changes to <
155
> and select
>.