The FJ400 has an optical Cell for triggering the FJ400 from another flash or strobe unit fired in near proximity. The Optical triggering is only available in Manual mode and will turn off all wireless radio signal reception for firing. It will also disable group and channel choice, power adjustment and HSS capabilities. If choosing Optical cell for triggering, an Eye icon will show up on the screen. After using optical triggering, remember to resume TTL-All in menu 1 of the FJ400 to restore Wireless Radio Transmission from FJ wireless triggers. When you power off the FJ400 the Eye icon will disappear and Optical cell triggering will be disabled. You must still activate the TTL- All function in menu 1 to resume standard radio controlled wireless triggering.
IMPORTANT: To avoid the FJ400 entering SLP (sleep mode) based on the Auto-off settings of the FJ400, while using the optical cell, enter the settings menu (menu 6) by long pressing the top menu button. Change the Auto-off setting to "OFF". Early firmware did not offer an "OFF" option so make sure to check your firmware version for updates if the "OFF" option is not given.