3.Readying the 550EX (Slave Setting)
(4)Channel Setting(1) Slave settingIPower on (2) Channel setting
*:RATIO
To prevent wireless signals from being transmitted to unrelated S p e e d l i t e 55OEX u n i t s i n t h e vicinity, you can set a channel dif- ferent from the one used by the unrelated Speedlite 550EX units. One of four channels can be set. T h e ST - E2 ( m a s t e r ) and s l a v e Speedlite(s) must be set to t h e same channel No.
P r e s s t h e < CH. > button a n d select the desired channel.
Each time the button is pressed the channel indicator changes 
1
T h e S T - E 2 a n d S p e e d l i t e 5 5 0 E X m u s t be set to the same channel No
S e t t h e w i r e l e s s selector t o
1 < SLAVE >. H e r e i n a R e r , a S p e e d l i t e 5 5 0 E X s e t to t h i s mode will be called a "slave."
The zoom setting is set automat- ically to (a c7'lmm. T h i s can be overridden manually.
2 Set the slave's main switch to < I > or < SE > to turn it on.
When t h e Speedlite is ready t o fire, the
E a c h t i m e you p r e s s t h e
<SEL/SET > button, the blink- ing display changes in the fol-
lowing loop: |
|
+ m + - - - - - | , |
|
2 While 
is blinking, press t h e < + z or < - > butlon to select the same channel No. as the
0 If t h e 550EX's channel No. is d i f f e r e n t f r o m t h e S T - E 2 ' s c h a n n e l No., w i r e l e s s t r a n s - mission will not work.