Canon 550 EX - Manual (Page 14)

4. Wireless Selector
The wireless selector has three settings as shown below.
Set to OFF to use the 550EX as a
normal, on-camera Speedlite.
Set to MASTER to use the 550EX as the
master unit in a wireless, multi-Speedlite
system.
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Set to SLAVE to use the 550EX as a
slave unit in a wireless, multi-Speedlite
system.
02. F073-E (9~) 02.4.1 2:08 PM Page 14