D4 Air Pack description from Profoto:
The pack has 4 outlets for flash heads that can be individually controlled with settings in f-stops or Ws displayed on 4 digital displays. Flash power is controllable over an 8 stop range in 1/10 or 1 stop increments. Modeling lights have 4 modes of control to help you pre-visualize your final shot and each head outlet can handle up to 500W. The D4 Air 2400 recycles in a speedy 0.09 to 2.2 seconds and has short enough flash durations to stop most active subjects. Choice of Normal or Fast recycling modes help you cope with even the most finicky electrical service.
While you can use the included sync cord to trigger the pack, the D4 has multiple ways to do it wirelessly. An Air radio receiver is built into the pack which is compatible with Profoto's Air Sync or Air Remote transceivers, either of which will trigger the pack at distances up to 980'. The D4's USB interface not only allows you to take advantage of firmware updates, but it also accepts the Air USB dongle which lets you control multiple packs wirelessly using Profoto's Studio 3 software or Capture One Pro plug-in. The D4 Air 2400 has a 100-240 VAC power supply for worldwide use and is compatible with virtually all current Profoto pack heads.