Sony a (alpha) SLT-A55VL - Manual (Page 120)

120
You can shoot using the SHUTTER and 2SEC (the shutter is released after
2 seconds) buttons on the RMT-DSLR1 Wireless Remote Commander
(sold separately). Also, refer to the operating instructions supplied with the
Wireless Remote Commander.
Shooting with the Wireless Remote Commander
1
on the control button t
(Remote Cdr.)
2
Focus on the subject, point the transmitter of the Wireless
Remote Commander to the remote sensor, and shoot the
image.