WhenTTL switch atA means flash A will can be worked as TTL mode; When TTL switch atB means flash B will can be worked as TTL mode; When TTL switch at C means flash C will can be worked as TTL mode.
Flash control switch for control A/B/C flash. When the switch is on status, that is mean the flash is working; when the switch isoff status, that is mean the flash is not working.
Caution: 1. When using the Canon camera and flash, group B flash cannot use as TTL mode. 2. Flash control switch must be on when using TTL mode.
TTL command switch at flash A, its works with TTL mode; flash B and C switch to on for support flash.
TTL command switch at flash A, its works with TTL mode; flash C switch to on for support flash; flash B switch to off for stop using.