Pentax 540FGZ - AF - Hot-shoe clip-on Flash Operating Manual page 50

(Using the AF540FGZ in Combination with
another AF540FGZ)
1
Firstly, set the wireless mode and channel of the
AF540FGZ attached to the camera, and register
the channel on the camera.
Turn the camera off and then attach the
AF540FGZ to the hot shoe of the camera.
Set the power switch of the flash unit to
(WIRELESS).
48
Press the wireless mode button (M/C/S) the
number of times required to select CONTROL
or MASTER.
CONTROL: For using the flash unit attached
to the camera as the control flash.
MASTER: For using both flash units as main
flashes.
Slide down the setting switch to the (yellow
dot) to display the channel on the LCD panel.
Press the channel button (CH) and select a
channel from 1CH to 4CH.