Wein PST-500-2 2 Channel Pro Sync Infrared Transmitter

The transmitter can be mounted on, and fired by any standard camera hot shoe (orconnected to a PC terminal for off-shoe use). Just slide the compact transmitteronto your camera; no cords, no antenna, nothing to clip to your belt. A pair of "AA" batteries in the transmitter powers up to 5,000 shots, with recycle times averaging less than a second - faster than most any flash- so your Pro-Sync is up and ready when you are.

Each time you shoot, the transmitter fires, and an "explosion" of coded infraredlight fills the room, bouncing off walls and around corners. You can't see the signal (neither can your film), but the Pro-Sync receiver can.