The Profoto Air Remote TTL-C is the key to wireless triggering and TTL remote control of its B1 and B2 AirTTL Off Camera Flash heads. Operating on the 2.4 GHz bandwidth, the transmitter, really a controller, has 8 frequency channels and with 3 groups per channel and a range of up to 330' for TTL triggering and 1,000' for normal triggering. Each channel has power ratio capability of +/- 2 stops. If you prefer to use manual you have +/- 9 stops power variation. You've also got modeling light, unit shut-down and first or rear curtain control. The TTL-C, the B1 500 AirTTL and B2 Off Camera Flashes have micro-USB connectors for firmware updates directly from Profoto's website, such as High Speed sync which allows sync speeds as short as 1/8,000 sec. Besides the B1 and B2, the Air Remote TTL-C will also manually remote trigger all Profoto Air packs and monolights but without the TTL feature.